Question

18.

Given that sin x =
8
and sin y = , where x and y are acute, find the value of cos (x + y).
17
A.
B.
130
221
140
221
140
204
220
22
C.
D.

Answer 1

B

Explanation:

`sin(x)=(5)/(13), cos(x)=\sqrt{1-((5)/(13))^2}=(12)/(13)`

`sin(y)=(8)/(17), cos(y)=\sqrt{1-((8)/(17))^2}=(15)/(17)`

`\cos(x+y)=cos(x)cos(y)-sin(x)sin(y)\\=(12)/(13)*(15)/(17)-(5)/(13)*(8)/(17)\\=(140)/(221)`