Find the Exact Value of the Given Trigonometric Function of the Angle

Multiple Choice

Find the exact value of the given trigonometric function of the angle $\theta$ shown in the figure. (Use the Pythagorean Theorem to find the third side of the triangle.)
Find: $\cos \theta$

A) $\frac { 8 } { 17 }$

B) $\frac { 15 } { 17 }$

C) $\frac { 8 } { 15 }$

D) $\frac { 15 } { 8 }$

E) $\frac { 17 } { 15 }$