### Home > INT3 > Chapter 7 > Lesson 7.2.3 > Problem7-81

7-81.

Eugene wants to use the cosine ratio to calculate $y$ in this triangle.

1. Which angle should he use to write an equation and solve for $y$ using the cosine ratio? Why?

He'll need the adjacent side and the hypotenuse. To which angle is $y$ adjacent?

2. Write an equation and solve for $y$ using cosine.

$\cos \left(29^\circ \right)=\frac{y}{42}$