Question

Help me with this I don’t know if I need to use law of cosines or law of sines to find the degree

Answer 1

Law of cosines

Explanation:

In this problem i need to use the law of cosines, because the angles are unknown.

we know that

The formula of the law of cosines is equal to

`c^2=a^2+b^2-2(a)(b)cos(C)`

where

`a=7\ units\\b=8\ units\\c=10\ units\\C=\theta`

substitute in the formula

`10^2=7^2+8^2-2(7)(8)cos(\theta)`

`100=49+64-112cos(\theta)`

`100=113-112cos(\theta)`

`112cos(\theta)=113-100`

`112cos(\theta)=13`

`cos(\theta)=(13)/(112)`

using a calculator

`\theta=cos^-1((13)/(112))`

`\theta=83.33\°`