Suppose ABC Is a Right Triangle with Sides of Length $\cos \mathrm { A }$

Multiple Choice

Suppose ABC is a right triangle with sides of length a, b, and c and right angle at C. Find the exact value of the indicated
trigonometric function. You may need to use the Pythagorean theorem to find the unknown side length. Rationalize the
denominator if necessary.
-Find $\cos \mathrm { A }$ when $a = 2$ and $b = 7$ .

A) $\frac { 7 \sqrt { 53 } } { 53 }$
B) $\frac { \sqrt { 53 } } { 2 }$
C) $\frac { 2 \sqrt { 53 } } { 53 }$
D) $\frac { \sqrt { 53 } } { 7 }$