Question

In DEF, given the lengths of the sides, find the measure of the stated angle to the nearest degree.

d = 10.7, e = 15.5, f = 16.2;

Answer 1

e=15.5 is going to be right

Answer 2

Using the Law of Cosines
cos(D) = (e² + f² -d²) ÷ (2ef)
cos(D) = (240.25 + 262.44 -114.19) / (2*15.5*16.2)
cos(D) = 388.50 / 502.20
cos(D) = 0.7735961768
D = 39.322 degrees

For the next angle we can use the Law of Sines
sin ∠E = (e • sin(D)) ÷ d
sin ∠E = (15.5 * 0.63368) / 10.7
sin ∠E = 0.9179476636
E = 66.628 Degrees

Angle F = 180 -39.322 -66.628 = 74.05 degrees