Answer:
D. 66.4
Step-by-step explanation:
So this problem uses SOHCAHTOA or the three trig functions.
Specifically this uses cosine, because it has an adjacent and a hypotenuse.
First you would determine what to do on the calculator, and since the problem is saying so, use the inverse cosine button. This will give you a angle measure from the decimal.
On a calculator, type in cos^-1(6/15). I used 6/15 because cosine is adjacent over hypotenuse. This will give you 66.4, which is D on the answers.