Two Sides of a Right Triangle ABC (C Is the Right

Multiple Choice

Two sides of a right triangle ABC (C is the right angle) are given. Find the indicated trigonometric function of the given
angle. Give exact answers with rational denominators.
-Find $\cos \mathrm { A }$ when $\mathrm { a } = 3$ and $\mathrm { b } = 7$ .

A) $\frac { \sqrt { 58 } } { 7 }$
B) $\frac { 7 \sqrt { 58 } } { 58 }$
C) $\frac { 3 \sqrt { 58 } } { 58 }$
D) $\frac { \sqrt { 58 } } { 3 }$