Question

If AABC is a triangle with mzC = 90°, which of the

following must be true about angles A and B?
OA.
1
sin A
O C.
=
O B. cos A = 1
tan A +
O D. sin A
sin B
=
1
tan B
cos B
cos B
=
1

Answer 1

D. sin(A) = cos(B)

Explanation:

You want to know the true relationship between trig functions of acute angles A and B in a right triangle.

Sine

The sine of angle A in right triangle ABC with C = 90° is ...

sin(A) = a/c

Cosine

The cosine of angle B in right triangle ABC is ...

cos(B) = a/c

These are the same expression, so we can declare ...

sin(A) = cos(B) . . . . . choice D

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