In ΔABC , angle C is a right angle. Which statement must be true?

A. sin A = cos B
B. sin A = tan B
C. sin B = tan A
D. sin B = cos B

 Choice A. sin(A) = cos(B)

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Explanation:

The rule is that sin(A) = cos(B) if and only if A+B = 90.

Note how

Since both result in the same fraction BC/AB, this helps us see why sin(A) = cos(B). Similarly, we can find that cos(A) = sin(B).

In the diagram below, the angles A and B are complementary, meaning they add to 90 degrees. So this trick only applies to right triangles.

The side lengths can be anything you want, as long as you're dealing with a right triangle.

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step-by-step explanation:

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