Question

DEF, find the length of d, to the nearest tenth, given that ∠D=110o, e = 10cm and f = 14cm.

Answer 1

d = 19.8 cm

Explanation:

Use the law of cosines

`d^(2) = e^(2) + f^(2) -2ef cos D\\d^(2) = 10^(2) + 14^(2) -2(10)(14) cos 110\\`

= 100 + 196 - 280 cos 110

= 296 - (-95.765640)

= 391.765640

`d = √(391.7656401)`

d = 19.8 cm