1 Answer

Rui Nunes · Answer 1 · 2020-06-17T21:14:19+0000

Answer:

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

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

$\theta=83.33\°$

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