Question

Please answer it now in two minutes

Answer 1

`f = 10.7`

Explanation:

Given ∆DEF,

<F = 36°

DF = e = 15

EF = d = 6

DE = f = ?

f can be found using the Law of Cosine as shown below:

`f^2 = d^2 + e^2 - 2(d)(e)*cos(F)`

Plug in your values:

`f^2 = 6^2 + 15^2 - 2(6)(15)*cos(36)`

Evaluate:

`f^2 = 36 + 225 - 180*0.809`

`f^2 = 261 - 145.62`

`f^2 = 115.38`

`f = 10.74`

`f = 10.7` (to nearest tenth)