Question

Find the cosine of ∠E.

image of a right triangle that has the following values, Angle C, Angle D, Angle E, Line CD which has a length of 15, Line DE which has a length of 17, and Line CE which has a length of 8

Answer 1

Since 8^2 + 15^2 = 17^2, the triangle is right with hypotenuse DE = 17 (so ∠C = 90°). For ∠E the adjacent side is CE = 8, so

cos ∠E = adjacent / hypotenuse = 8/17.