# The point (15, 20) is on the terminal side of an angle drawn in standard position. How do you find the exact value of the cosine of the angle?

Oct 19, 2015

Find cos of an angle x.

Ans: $\cos x = \frac{3}{5}$

#### Explanation:

Call x the angle to be determined:
$\tan x = \frac{y}{x} = \frac{20}{15} = \frac{4}{3.}$
The hypotenuse h of the right triangle with 2 sides x and y is:

h^2 = x^2 + y^2 = 9 + 16 = 25 --> h = 5.
$\cos x = \frac{x}{h} = \frac{3}{5}$