Question

. A triangle has side lengths of 8, 7, and 14. To the nearest tenth of a degree find the measure of the angle opposite the side of length 8.

Answer 1

Given:

The measure of three sides of a triangle are 8, 7 and 14.

To find:

The measure of the angle opposite the side of length 8.

Solution:

According to the Law of Cosine:

$\cos A=\dfrac{b^2+c^2-a^2}{2bc}$

Let a=8, b=7 and c=14, then by using Law of Cosine, we get

$\cos A=\dfrac{7^2+14^2-8^2}{2(7)(14)}$

$\cos A=\dfrac{49+196-64}{196}$

$\cos A=\dfrac{181}{196}$

Taking cos inverse on both sides.

$A=\cos^{-1}\dfrac{181}{196}$

$A=22.561328$

$A\approx 22.6$

Therefore, the measure of the angle opposite the side of length 8 is 22.6 degrees.