Chapter 8.5, Problem 21WE

To determine

To find: the base angle of isosceles triangle.

Answer to Problem 21WE

The base angle of isosceles triangle is $65°$ .

Explanation of Solution

Given:

The base and altitude of isosceles triangle are 70 cm and 75 cm respectively.

Calculation:

Altitude of an isosceles triangle bisects the base of the triangle.

Hence, the triangle is shown below:

Base angles ABC and ACD are equal for isosceles triangle.

The base angle of isosceles triangle is calculated as follows:

  $\begin{array}{c}\tan \angle ABC=\frac{\text{Height}}{\text{Base}}\\ \tan \angle ABC=\frac{\text{75}}{35}\\ \angle ABC\approx 65°\end{array}$

Thus, the base angle of isosceles triangle is $65°$ .