help!

Solution:

Since x and y are complementary they add up to 90degrees or PI/2 rads. 

\(x+y = 90 \rightarrow (1)\)

rearranging the terms we get:

 \(y= 90-x\)

Taking the sin on both sides we get the following identity:

\(sin(y) = sin(90-x) \)

\(\Rightarrow sin(90)cos(x) - cos(90)sin(x)\)

\(\Rightarrow (1)(cos(x)) - (0)(sin(x)) \)

\(\Rightarrow cos(x)\)

\(\Rightarrow -0.3\)

\(Answer: sin(y) = -0.3\)