Question

Find the cosine of F in the triangle below. Rationalize the denominator, if necessary.

A. 1 / square root of 15
B. 4 square root of 15 / 15
C. 4
D. square root of 15 / 15

(picture below has the multiple choice answers as well)

Answer 1

cos∠F = √15/15 ⇒ answer (D)

Explanation:

∵ cos∠F = EF/FG

∵ EF = 2

∵ FG = 2√15

∴ cos∠F = 2/2√15 = 1/√15 ⇒ multiply yp and down with √15

∴ cos∠F = √15/15 ⇒ answer (D)