Question

What is cosA ?



Enter your answer, as a simplified fraction, in the box.

Answer 1

5/13

Explanation:

From the mnemoic SOH CAH TOA, we know that ...

... Cos = Adjacent/Hypotenuse

In this triangle, that means ...

... cos(A) = AC/AB

We are given the value of AC, but we need to find the value of AB. We can do that using the Pythagorean theorem:

... AB² + AC² +BC²

... AB² = 15² +36² = 1521 = 39²

... AB = 39

Then ...

... cos(A) = 15/39 = (5·3)/(13·3)

... cos(A) = 5/13