Use the figure below to find the exact value of the trigonom

Use the figure below to find the exact value of the trigonometric function cos 2.

A.    B.    C.    D.

Solution

soltuion:

from triangle

sin() = 8/17

cos() = 15/17

multiply above

sin() * cos() = 120 /289

multiply 2 on both side

2 sin() cos() = 240 /289

sin (2) = 240 /289

squarng both side

sin² (2) = (240 /289)²

1-cos²(2)= (240 /289)²

cos(2) = 161/289

option (C) is correct = 161/289