Nguoithay.vn cos2a = cos2a sin2a = 2cos2a = 2sin2a sin2a = 2.sina.cosa 2.tana tan2a = - tan2a cos(a + b) = cosa.cosb sina.sinb cos(a - b) = cosa.cosb + sina.sinb sin(a + b) = sina.cosb + cosa.sinb sin(a - b) = sina.cosb - cosa.sinb tana + tanb tan(a + b) = - tana.tanb tana - tanb tan(a - b) = + tana.tanb cos2a = sin2a = cos 2a - cos2a a + b a - b cos 2 a - b a + b sin cosa - cosb = -2.sin 2 a + b a - b sina + sinb = 2.sin cos a - b a + b sin sina - sinb = 2.cos 2 sin(a b) tan a tan b cosacosb cosa + cosb = 2.cos tan a tan b sin(a b) cosacosb cosa.cosb = [cos(a sina.sinb = [cos(a b) + cos(a + b)] b) - cos(a + b)] sin acosb= cosa sinb= Nguoithay.vn sin( a b) sin( a b) sin( a b) sin( a b) Nguoithay.vn -180o -150o -2 cos -1 3 135o 2 2 tan 3 1 x d sin cot -6 - || 3 120o -6 2 3 -45o -30o 30o 45o 60o 90o 120o 135o 150o -1 2 -2 2 3 2 2 -2 2 2 Error -2 2 || 3 Error || -1 3 || 3 -1 90o -3 -4 -60o -1 -1 - 3 II.CÁC PH -1 a 1) x arcsina+k2 ;k x arcsina+k2 sinx = a sinx = x=k ;k sinx = x = + k2 ; k x +k2 ;k +k2 x x +k2 ;k +k2 x Z 1) x arccosa+k2 ;k x arccosa+k2 cosx = x=2 +k ;k cosx = cosx = -1 x = k2 ; k Z x = + k2 ; k Z +cosx = cos Z Z \ + t anx=a tanx=1 tanx=-1 t anx=0 Nguoithay.vn k ,k x=arctana+k ,k x= x=- + tanx=tan k ,k x=k , k Z ( a = sin ) Z ( -1 a cosx = a +sinx = sin Z x = -2 + k2 ; k sinx = -1 Z k ,k x= +k ,k Z ( a = cos ) 180o -1 || Nguoithay.vn \ k ,k + co t x=a + cotx=cot x=arccota+k ,k cotx=1 x= k ,k cotx=-1 x=- co t x=0 x= x= +k ,k k ,k k ,k a b2 ) a b c sinx+ cosx= 2 2 a b a b a b2 a cos = a b2 b sin a b2 c s inxcos cosx sin a b2 c sin( x ) a b2 *Chú ý c2 a b2 u a.b 0, c thì: a sin x b cos x tan x b a asin x b sinxcosx+ccos2 x (1) a = 0: b sinxcosx+ccos2 x cosx=0 cosx(bsinx+ccosx)=0 bsinx+ccosx=0 c = 0: asin2 x b sinxcosx=0 sinx(asinx+bcosx)=0 a 0, c 0,cos x : (1) sinx=0 asinx+bcosx=0 sin x sinxcosx cos x b c cos x cos x cos x a tan x b t anx+c=0 a Bài a) cot(5 x b) 2cos2 x c) d) sin x sin x 2cos2 x ) sin 3x cos3x Nguoithay.vn cos x Nguoithay.vn a) cot(5 x 5x ) cos x b) 2cos x cos x x cos x k x k x k ,k k2 c) sin 3x cos3x sin (3x ) = sin 3x cos 3x 2 2 d) sin x sin x 2cos x sin x sinx ( cosx sinx ) = tan x 3x k2 x k2 x k x arctan k Bài a) tan(3x ) 5 3x x k x sin x 1 sin x 2 b) 2sin x sin x c) sin 5x cos5x sin x cos x sin (5 x k2 )= - 5x d) 3sin x sin x cos x 2sin xcos x 2cos x x cos x tan x x x sin x 1 f 3sin x cos x x x 2cos x(sin x cos x) k2 k e cos2 x 3sin x 2sin x 3sin x Nguoithay.vn k2 , k 2 sin x k2 x x k 2sin x 3sin x k2 k2 , k k2 sin x cos x 2 2 4 k2 x 20 k2 Nguoithay.vn sin x cos x cos xsin 2 k2 sin( x ) sin k2 12 ,k x k2 x k2 12 g 3sin x cos x sin x cos x 2 2 sin( x ) sin sin x cos cos xsin 6 x k2 x k2 12 ,k 11 x k2 x k2 12 h 2cos2 x 3cos x 4cos2 x 3cos x x k2 cos x ,k 1 cos x x arccos( ) k 4 2 i 2sin x 3sin xcos x 5cos x 2ta n x 3ta n x 4 tan x tan x x x k x arctan( ) k ,k Bài a 3sin x sin x b 2sinx 2cos x c sin x sin3x sin5x d sin x sin3x sin5x cos x cos3x cos5x e 2sin x 5sin xcos x 4cos2 x f 2cos2 x 3sin x h tan x.tan5x g sin 2 x cos2 3x i 5cos2x 12sin 2x 13 j 2sin x 5cos x k 2cos x 3sin x Bài b (3 cot x)2 5(3 cot x) a tan x cot x d 4sin x 3sin x 2cos x f 4sin x 12cos2 x c 3(sin3x cos x) 4(cos3x sin x) e sin x sin 2 x sin 3x sin x Bài Giải phương trình sau : a) cot(5 x b) 2cos2 x c) Bài giải : d) sin x sin x 2cos2 x ) sin 3x cos3x Nguoithay.vn cos x Nguoithay.vn a) cot(5 x 5x ) k b) 2cos2 x cos x cos x x cos x k x k x k2 c) sin 3x cos3x Sin (3x ) = sin 3x cos 3x 2 2 d) sin x sin x 2cos x sinx ( cosx 3x k2 x k2 sin x tan x sinx ) = x k x arctan k Bài giải phương trìnhlượng giác : ) a) tan(3x 3x x k x b) 2sin x sin x sin x x 5x 2 k2 1 sin x cos x 2 k2 x 20 d) 3sin x sin x cos2 x k2 x c) sin 5x cos5x k2 sin x k k2 Sin (5 x x cos x tan x )= - k x k au: a 2sin x b 2cos x x a) sin x sin b) cos x cos Nguoithay.vn x x 6 c cos 2x 3sin x x k2 k2 x k2 x 6 k2 l2 l2 d sin x cos x Nguoithay.vn c) 2sin x 3sin x sin x sin x a 2sin x b 2cos x 0 x a) sin x sin x 3 b) cos x cos x 3 c) 2sin x 3sin x sin x sin x x k2 k2 x k2 x d) 6 12 x 12 b 2cos x a) sin x sin x b) cos x cos 6 x 4 c) 4cos2 x 3cos x cos x Nguoithay.vn k2 k2 2 k2 k2 d sin x cos x x k2 x arccos k2 sin x cos x 2 x k2 12 11 x k2 12 d) a sin x cos x c cos2x + sinx +1=0 k2 c cos2x -3cosx +1 =0 k2 k2 d sin x cos x sin x cos x 2 x x 2 c cos 2x 3sin x 2 a 2sin x cos x sin x cos x 2 x k2 12 11 x k2 12 d) b cos 2x 3sin x k2 2 2 Nguoithay.vn k2 12 11 x k2 12 x sin x cos x 2 a/ 2 sin x sin x sin x b 2sin x 3sin x sin x x x x c x 6 k2 l2 l2 k k Câu b.sin2x +3sinx cosx -5 cos2x= a cos 2x 3sin x c.2 cos2x -3cosx +1 =0 x sin x a 2sin x 3sin x x sin x x b t sin x cos x, sin x.cos x t x x 6 l2 l2 2 t t 12t 11 PT c t 2 k2 x 11 x k2 k2 k2 k2 câu 2cos x b.sin2x +3sinx cosx -5 cos2x= a/ Nguoithay.vn 2cos x cos x cos x x k2 k2 Nguoithay.vn t sin x cos x, b/ t 12t 11 sin x.cos x t2 PT 2 t (0,25) t (0,25) (0,25) (0,25) 11 x k2 (0 k2 x a 2sin x 3sin x b 3sin x sin 2x c 2sin x 2cos x x x k2 k2 b x=k3600 x c x k 24 13 k 24 a tan(x +200) = b sinx + sin2x = cosx + cos3x c.4sin2x -5sinx cosx -6 cos2x= DS a x=100 +k1800 x b x k2 k a sin x cos x x c arctan k x arctan( ) k b cos 2x 3sin x 2 k2 12 11 x k2 12 x 1a) sin x cos x 2 2 sin x 1b) 2sin x 3sin x Nguoithay.vn sin Nguoithay.vn x sin x sin x (0,25) x 6 x k2 (0,25*2) l2 l2 tan x tan x Câu 12 a sin(3x 2x b 2x ) 0(0.25) k2 k2 b.sin(2x + 3x k (0.25), x 18 x k 24 (0.25* 4) 11 x k 24 2cot x 5co t x Câu 13 a cos(3x ) 0(0.25) ) =- b.cos(2x + 3x ) =- k (0.25), x 2 k (0.5) c cos2 x 3sin 2 k (0.5) 18 cos x x k 3 cot x k x arc cot 2x b 2x k2 4 k2 x x 24 24 k (0.25* 4) k c cos x cos x 3cos x x 2k 2x arccos( cos x x k ) 2k x k Z 1 arccos( ) k 5sin x sin x Nguoithay.vn h cos7 x sin5x 10 3(cos5x sin 7x) Nguoithay.vn 84 11 x 84 k x Bài cos7 x sin x k Bài 3(sin5x cos x) 4(sin x cos5x) 3sin5x 4cos5x 4sin x 3cos x 4 sin5 x cos5 x sin x cos x 5 5 cos , sin ) sin5xcos cos5 xsin sin xsin cos xcos , ( 5 sin(5x ) cos( x 5x 5x sin(5 x ) x k2 x x k2 cos9 x 4sin 3x Bài 3sin3x sin9 x cos9 x (1) x 12 x k ) x k (3sin3x 4sin 3x) sin(9 x Bài tan x sin x cos x 2(2cos x cos x ) sin( ) sin cos9 x x k 18 x k 54 ) (1) cos x k sin x sin x cos x 4cos x cos x cos x sin x 2sin xcos2 x cos2 xcos x 2(2cos x 1) sin x(1 2cos2 x) cos2 xcos x 2cos2 x sin xcos2 x cos2 xcos x 2cos2 x cos x cos2 x(sin x cos x 2) x sin x cos x 2(vn) Bài 8sin x cos x (*) Nguoithay.vn k (*) sin x sin x 8sin xcos x x k 3sin x cos x 4(1 cos2 x)cos x 11 3sin x cos x Nguoithay.vn 4cos2 xcos x cos3x cos x C2 (*) 8sin xcos x 3sin x 3cos x sin x 2(cos3x cos x) x cos3x cos( x 3sin x cos x 3sin x 3cos x 4cos3 x 3cos x cos x sin x 2 cos3x cos( x x k 12 Bài 9sin x 6cos x 3sin x cos2 x 6sin xcos x 6cos x 2sin x 9sin x 6cos x(sin x 1) (sin x 1)(2sin x 7) (sin x 1)(6cos x 2sin x 7) sin x x k2 6cos x 2sin x Bài sin x 2cos2 x sin x 4cos x 2sin xcos x 2(2cos2 x 1) sin x 4cos x sin x(2cos x 1) 4cos x 4cos x sin x(2cos x 1) (2cos x 1)(2cos x 3) (2cos x 1)(2sin x 2cos x 3) cos x x k2 2sin x 2cos x 3,(vn) Bài 2sin x cos2 x 7sin x 2cos x 4sin xcos x (1 2sin x) 7sin x 2cos x 2cos x(2sin x 1) (2sin x 7sin x 3) 2cos x(2sin x 1) (2sin x 1)(sin x 3) (2sin x 1)(2cos x sin x 3) k2 x x Bài sin x cos2 x 3sin x cos x Nguoithay.vn k2 12 k x k 12 3sin x cos x 6cos x 8cos3 x k 2sin x 2cos x sin x 3,(vn) ) 8(1 cos2 x)cos x 8cos x 8cos3 x x 3sin x 3cos x 3sin x cos x ) Nguoithay.vn 2sin xcos x (1 2sin x) 3sin x cos x (2sin xcos x cos x) (2sin x 3sin x 1) cos x(2sin x 1) (2sin x 1)(sin x 1) 2sin x (2sin x 1)(cos x sin x 1) cos x sin x x x 2sin x cos x sin x t sin x k2 cos( x t ) x cos x 2( sin x cos2 x, t t t x k2 2 cos x) cos(2 x Bài 10 (sin x Ta có: sin x k2 k2 ) cos x) 2cos(2 x t t 2t t 10 t ) 5 : 2 : 2cos(2 x ) 12 x k 2cos3 x 2cos2 x sin x Bài 11 2cos3 x cos2 x sin x 2cos2 x(cos x 1) (1 sin x) 2(1 sin x)(cos x 1) (1 sin x) 2(1 sin x)(1 sin x)(cos x 1) (1 sin x) (1 sin x)[2(1 sin x)(cos x 1) 1] (1 sin x)[1 2sin xcos x 2(sin x cos x)] sin x 1 2sin x cos x 2(sin x cos x) sin x x k2 2sin xcos x 2(sin x cos x) (sin x cos x)2 2(sin x cos x) (sin x cos x)(sin x cos x 2) sin x cos x tan x Nguoithay.vn x k 13 Nguoithay.vn cos x (*) sin x x k sin 2 x cos x cos x (*) cot x 1 cot x cos 2 x sin x cos x cos x sin x(1 cos2 x) cos2 x(1 cos2 x) sin x sin xcos2 x cos2 x(1 cos2 x) cos2 x(sin x cos2 x 1) cos x sin x cos x Bài 12 cot x cos x x k x sin x cos2 x sin(2 x ) sin( ) x k k x k 3sin x Bài 13 4(sin x cos4 x) 4[(sin x cos2 x)2 2sin xcos2 x] 3sin x 2 4(1 sin x) sin x cos4 x 3sin x x x k k 12 2 sin x 2 sin x 2(sin x cos2 x)(1 sin xcos2 x) (2 sin x) (sin x cos2 x)(2 sin x) (2 sin x)(sin x cos2 x 1) sin x cos2 x Bài 14 sin x cos3 x sin(2 x ) 2 Bài 15 tan x 3cot x 4(sin x (*) x x k k cos x) (*) sin x x k sin x cos x 4(sin x cos x) cos x sin x sin x 3cos2 x 4sin xcos x(sin x cos x) (sin x Nguoithay.vn cos x)(sin x cos x) 4sin xcos x(sin x 14 cos x) Nguoithay.vn (sin x cos x)(sin x sin x sin x cos x 4sin xcos x) cos x cos x 4sin x cos x sin x cos x sin x cos x 4sin xcos x tan x sin x sin x x k 2sin x sin x cos x x cos x sin x sin( x ) x k2 k k 3 Bài 16 sin x cos x sin x cos x sin x(sin x 1) cos3 x cos x sin xcos2 x cos3 x cos x cos x( sin xcos x cos x 1) cos x sin x cos x cos x x cos x x k ;x k sin xcos x cos2 x 1 cos x sin x 2 1 sin x cos2 x 3,(vn) x k ,k 1 ) (1 cos x)2 [1 cos(2 x Bài 17 cos x sin ( x 4 4 sin x cos2 x (1 cos2 x)2 (1 sin x) cos(2 x ) cos 4 x 2 )]2 k2 x k Bài 18 4sin3 xcos3x 4cos3 xsin3x 3 cos4 x 4sin x(4cos3 x 3cos x) 4cos3 x(3sin x 4sin x) 3 cos4 x 12sin3 xcos x 12cos3 xsin x 3 cos4 x 4sin xcos x(cos2 x sin x) cos4 x 2sin xcos2 x Nguoithay.vn cos4 x sin x 15 cos4 x Nguoithay.vn sin x cos x 2 x sin(4 x ) sin Bài 19 k 24 x k ,k 2 2sin x sin xcos x cos x m (*) -1 (*) (1 cos x) a 1 sin x (1 cos x) m sin x 3cos2 x 2m 2 c a b2 4m2 4m (1 2m)2 10 m 10 b.Khi m = -1 sin x 3cos2 x sin xcos sin(2 x sin x 10 3 cos x 10 10 cos , sin , ( 10 10 cos2 xsin 2x 2x ) sin sin x 4sin( Bài 20 x k k2 k2 x) tan tan sin ) x (*) x) sin( x) cos x 2 tan tan cos 3sin ,cos tan 4cos x (*) 3sin 3sin sin x 4cos x (**) sin x Ta có: sin( a 3sin x 4cos x sin x cos Nguoithay.vn sin x cos x 5 cos xsin 1,( cos , sin ) 5 16 k Nguoithay.vn sin( x ) x cos (3sin ) 16 25 cos sin 2 k2 cos sin 2 1 cos Bài 21 a 2(sin x cos x)cos x cos2 x b (2cos x 1)(sin x cos x) c 2cos x d 3sin x e 2cos3x g cos x 6(cos x sin x) f cos x 3sin x cos x 3 sin x cos x sin x k cos7 xcos5x h sin x cos x cos2 x cos3x j 3cos x 4sin x m cos2 x p 3sin x sin x x 3)cos x 2sin ( ) 2cos x msin x m 2cos x m=1 Bài 22 Bài 23 q tan x sin x cos x mcos x m 2sin x 2sin x cos x sin x 2cos x m Bài 24 cos3x sin 3x ) cos x 2sin x sin x Nguoithay.vn n 4sin x 3cos2 x 3(4sin x 1) (*) sin x mcos x m Bài 5(sin x 3sin x sin x cos x sin x 6 3cos x 4sin x 3sin x sin xsin5 x l 4(cos4 x sin x) 3sin x i 4sin3 x 3sin x (2 cos x x x m (1) k 12 ,k k 12 17 (*) (*) 4cos x cos x k Nguoithay.vn cos3x sin3x sin x 2sin xsin x cos3x sin3 x ) 2sin x 2sin x sin x cos x cos3x cos3x sin 3x 2sin x (sin 3x sin x) cos x 2sin x cos x cos x 5 2sin x 2sin x (2sin x 1)cos x 5cos x 2sin x (1) 5cos x cos2 x 2cos2 x 5cos x cos x x k2 1 (1 cos6 x)cos x (1 cos x) Bài cos2 3xcos2 x cos2 x 2 cos6 xcos2 x (*) Cách 1: (*) (4cos3 x 3cos2 x)cos2 x 4cos4 x 2cos2 x Ta có: 5(sin x cos2 x x k sin x Cách 3: (*) Cách 4: (*) cos8x cos4 x 2cos2 x cos4 x Cách 2: (*) (cos8 x cos x) cos4 x cos6 x cos x cos6 x cos x 1 (cos8 x cos x) cos8x cos4 x Bài cos x sin x cos( x )sin(3x x k cos8x cos4 x ) 3 [sin(4 x ) sin x] 2 2 sin x ( cos x sin x) 2 2 1 sin x (1 2sin 2 x) sin x 2 2 (sin x cos2 x)2 2sin x cos x sin 2 x sin x sin x Bài 5sin x 3(1 sin x) tan x cos x Nguoithay.vn x (1) k 18 x k Nguoithay.vn sin x sin x (1) 5sin x 3(1 sin x) 5sin x 3(1 sin x) cos x sin x 3sin x sin x 2sin x 3sin x 5sin x 2 sin x x x Bài 2sin 3x k2 k2 sin x sin x (*) cos x 2cos3x x k 2(sin 3x cos3 x) (*) sin x cos x 2[3(sin x cos x) 4(sin x cos3 x] sin x cos x 2(sin x cos x)[3 4(sin x sin x cos x cos x)] sin x cos x sin x cos x sin x cos x sin x cos x (sin x cos x)( 8sin x cos x ) sin x cos x (sin x cos x)(4sin x 2) sin x (sin x cos x)(4sin 2 x 2sin x 2) 2(sin x cos x)( 4sin x cos x) x sin x cos x 4sin 2 x 2sin x tan x sin x sin x x 1/ x Bài cos x(2sin x 2) 2cos x 1 sin x sin x (*) x 2cos2 x cos x Nguoithay.vn cos x 19 2 x k k 12 k 12 k 2sin xcos x cos x 2cos x 1 sin x (*) k Nguoithay.vn x k ,k 3x x x 3x Bài cos x cos cos sin xsin sin 2 2 1 cos x(cos x cos x) sin x(cos x cos x) 2 cos xcos2 x cos2 x sin xcos2 x sin xcos x cos2 x(sin x cos x) sin x sin xcos x cos2 x(sin x cos x) sin x(sin x cos x) (sin x cos x)(cos2 x sin x) (sin x cos x)( 2sin x sin x 1) sin x cos x 2sin x sin x x tan x sin x x k k2 sin x / 2 k2 6 4cos3 x sin xcos x 8cos x Bài 4cos3 x sin x 8cos x 2cos x(2cos x sin x 4) 2cos x(2sin x sin x 2) x k2 x Bài cos(2 x x 2 sin x k2 x ) cos(2 x k cos x x k2 ) 4sin x 2cos x cos 4sin x 2 2(1 2sin x) 4sin x 2 2 sin x (4 sin x Nguoithay.vn 2(1 sin x) sin x sin x 2)sin x x x k2 k2 20 Nguoithay.vn Bài 10 3cot x 2 sin x (2 2)cos x sin x x k cos x cos x (1) 2 (2 2) sin x sin x t t t cos x sin x cos x : sin x (1) 3t (2 2)t 2 t cos x sin x 2cos2 x 3cos x 3cos x 2(1 cos2 x) cos x x k2 2: cos x 2 2 cos2 x cos x 2(1 cos2 x) cos x t x x k2 , x 4sin 2 x 6sin x 3cos x Bài 11 cos x cos x (*) cos x 2 k2 k2 (*) x k 4(1 cos2 x) 3(1 cos2 x) 3cos x cos x 2 x x x 4cos2 x 6cos x k k k Bài 12 cos x cos3x 2cos5x (cos5x cos x) (cos5x cos3x) 2cos3xcos2 x 2cos4 xcos x (4cos3 x 3cos x)cos2 x (2cos2 x 1)cos x cos x[(4cos2 x 3)cos2 x 2cos 2 x 1] cos x{[2(1 cos2 x) 3]cos2 x 2cos 2 x 1} cos x(4cos2 x cos2 x 1) Nguoithay.vn 21 Nguoithay.vn x cos x cos x cos x 17 x x 17 arccos arccos k 17 17 k2 k2 17 (*) cos2 x 16 sin8 x cos8 x (sin x cos4 x)2 2sin xcos4 x Bài 13 sin8 x cos8 x [(sin x cos x)2 sin x sin 2 x sin x 2sin x cos x)]2 sin x) sin x (*) 16(1 sin 2 x sin x) 17(1 sin 2 x) sin 2 x 2sin 2 x cos4 x 5x x 5cos3 xsin Bài 14 sin (*) 2 x cos cos x x k2 (1 sin( 5k ) cos (*) sin( 2sin x sin 2 x x k ) x x x x 5x (sin 3x sin x) cos 5cos3 xsin cos 2 2 3sin x 4sin3 x 2sin xcos x 5cos3 xsin x sin x(3 4sin x 2cos x 5cos3 x) sin sin x(5cos3 x 4cos2 x 2cos x 1) x k sin x x k2 cos x cos x cos x Nguoithay.vn k 21 10 21 10 x arccos x arccos 21 10 21 10 22 k2 k2 cos xsin x Nguoithay.vn x k2 , x x arccos 21 10 21 10 Bài 15 sin x(cot x tan x) 4cos2 x k2 k2 (1) x k sin x cos x arccos x k cos x sin x cos x cos x sin xsin x Ta có: cot x tan x sin x cos x sin x cos x cos x (1) 2sin x cos x 4cos x sin x cos x cos2 x 2cos2 x cos2 x(1 2cos x) cos x cos x cos x / x k x x cos x sin x cos x k k ,x k 6x 8x 3cos 5 12 x 4x 4x 4x 4cos3 (1 cos ) 2(2cos 3cos 1) 5 5 4x t cos , t t 6t 3t 4t 21 t 4x cos x k 4x 21 21 x k cos arccos 4 5 21 arccos k x k , x 4 2 ) tan x (1) Bài 17 tan3 ( x Bài 16 2cos2 Nguoithay.vn 23 2(2cos 4x 1) Nguoithay.vn cos x cos( x x ) (tan x 1)3 (1 tan x)3 (1) x k k (tan x 1)3 (tan x 1)(1 tan x)3 tan x (tan x 1)[(1 tan x)3 (tan x 1)2 ] (tan x 1)(tan3 x 2tan x 5tan x) tan x(tan x 1)(tan x 2tan x 5) x k tan x tan x t C2: Bài 18 x x 4 sin x cos4 x tan( k x) tan( sin( sin( 4 cos4 x (1) x) x)cos( x)cos( 4 x) x) sin( sin( 4 x) cos x x) tan x tan x 4 tan x tan x 2sin 2 xcos2 x cos4 x (1) sin x cos4 x cos4 x 1 sin x cos4 x (1 cos2 x) cos4 x 2 2cos4 x cos2 x cos2 x tan( x) tan( x) cos2 x sin x x k Bài 19 48 cos4 x sin x 2 (1 cot x cot x) 2x sin (*) x k cos x cos x Ta có: cot x cot x sin xsin x Nguoithay.vn x k cos xsin x sin xsin x sin x cos x 24 Nguoithay.vn cos x 2sin x cos x (*) 48 cos4 x 2sin x sin x cos4 x 48 cos4 x x k x sin x 2sin 2 x 3sin x 48sin xcos4 x sin x cos4 x 6sin x sin 2 x sin x sin 2 x k Bài 20 sin8 x cos8 x 2(sin10 x cos10 x) cos x sin8 x(1 2sin x) cos8 x(2cos2 x 1) cos x sin8 x cos x cos8 xcos x cos x 4cos x(cos8 x sin8 x) 5cos x 4cos x(cos4 x sin x)(cos4 x sin x) 5cos x 4cos2 x(cos2 x sin x)(cos2 x sin x)(cos4 x sin x) 5cos2 x 4cos x(cos2 x sin x)(1 sin x) 5cos x 2 4cos2 x(1 sin x) 5cos x 4cos x(4cos x 2cos xsin 2 x 5) 4cos x[4cos x 2cos x(1 cos2 x) 5] 4cos x(2cos3 x 2cos x 5) Nguoithay.vn 25 cos2 x x k ...Nguoithay.vn -180o -150 o -2 cos -1 3 135o 2 2 tan 3 1 x d sin cot -6 - || 3 120o -6 2 3 -45o -30o 30o 45o 60o 90o 120o 135o 150 o -1 2 -2 2 3 2 2 -2 2 2 Error -2 2 || 3... (sin x cos2 x)(2 sin x) (2 sin x)(sin x cos2 x 1) sin x cos2 x Bài 14 sin x cos3 x sin(2 x ) 2 Bài 15 tan x 3cot x 4(sin x (*) x x k k cos x) (*) sin x x k sin x cos x 4(sin x cos x) cos x sin x... 12cos3 xsin x 3 cos4 x 4sin xcos x(cos2 x sin x) cos4 x 2sin xcos2 x Nguoithay.vn cos4 x sin x 15 cos4 x Nguoithay.vn sin x cos x 2 x sin(4 x ) sin Bài 19 k 24 x k ,k 2 2sin x sin xcos x cos