30.54
Which relationship in the triangle must be true?
sin(B) = sin(A)
sin(B) = cos(90 -B)
cos(B) = sin(180 - B)
cos(B) = cos(A)

Explanation:

The rule is that

sin(A) = cos(B)

if and only if A+B = 90.

Solving for A gets A = 90-B

So we end up with

sin(90-B) = cos(B)

which is the same as

cos(B) = sin(90-B)

the answers c

mathpapa

step-by-step explanation: