Question

The value of cos thita cos(90- thita) minus sin thita sin(90- thita) is:
A) 1
B) 0
C) 2
D) -1

Answer 1

(90°-ϴ) pertains to first quadrant wherein sine changes to cosine with positive sign and vice versa, if the angle is 90°- ϴ.

So​​​, sin(90°-ϴ) = cos ϴ and vice versa. Hence, on substituting the values the answer is zero.
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