... otherand to the base of the block. The other two sides are inclined at an oblique angle with the base. Angle C is a compound angle formed by the intersection of these two inclined sidesand the ... 270 ± θ column in Table 1. Because cos(270 ± θ) in the fourth quadrant is equal to ± sin θ in the first quadrant, find sin 66°40′ in the trig table. Therefore, cos 336°40′ = sin 66°40′ = 0.918216.Angle ... use the keys labeled sin−1, cos−1, and tan−1. On some other calculators, the sin, cos, and tan are used in combination with the INV, or inverse, key to find the num-ber corresponding to...