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

Cosine stands for "complementary sine."  The sine of an angle is the cosine of the complementary angle and vice versa.  Complementary angles add to 90°.

sin(B) = cos(90 - B)

It's true for any angle, and it doesn't have much particularly to do with a triangle.

=

x=0.8898305 is the answer to that equation

yep b and c r the correct got it! : )