Chapter 15, Problem 15CR

To determine

To Find: The area of an equilateral triangle.

Answer to Problem 15CR

  $20.78unit{s}^2$

Explanation of Solution

Given:

  $\text{Height of an equilateral triangle is}=6$

Formula Used:

  $\text{Pythagoras Theorem}:h^2=b^2+p^2$

  $A=\frac{1}{2}bh$

Calculation:

  $\begin{array}{l}\text{Exterior angle}=180-160={20}^o\\ \text{⇒}{S}_e=360\\ \text{⇒}\frac{360}{20}=18\\ \text{⇒}d=\frac{18\left(18-3\right)}{2}=135\end{array}$

Conclusion:

Thus the area of sector is $20.78unit{s}^2$ .