Question

If sin 20 degree=a and cos20 degree=b then which of the following represents the correct value of sin 70 degree in terms of a and/or b?
1) a+b
2) a
3) b
4)a-b

Answer 1

ANSWER

3) b

EXPLANATION

Given that:

$\sin(20 \degree) = a$

and

$\cos(20 \degree) = b$

Recall that the sine and cosine functions are equal for complementary angles.

This implies that,

$\sin(70 \degree) = \cos(20 \degree)$

$\sin(70 \degree) = b$