Question

A triangle has two angles measuring 69 and 77. Determine the measure of the third angle b

Answer 1

`m\angle B=34\°`

Explanation:

Given measures of 2 angles of a triangle :

m∠A = 69°

m∠C = 79°

Find m∠B.

We know that sum of angles of a triangle =180°

So, we have

`m\angle A+m\angle B+m\angle C=180\°`

Substituting the vales of m∠A = 69° and m∠C = 79°

`69\°+m\angle B+77\°=180\°`

Adding like terms.

`m\angle B+146\°=180\°`

Subtracting both sides by 146°.

`m\angle B+146\°-146\°=180\°-146\°`

∴
`m\angle B=34\°` (Answer)