Chapter 5, Problem 2GRFC

To determine

To find: Themeasure of $m\angle RST$ by using the given figure.

Answer to Problem 2GRFC

  $m\angle RST=55$

Explanation of Solution

Given:

  

Since $RS=RT$ and $\angle SRT=70$ in the given triangle, it has to find $m\angle RST$ .

  $RS=RT$ so, $\angle RST=\angle RTS$

Let $\angle RTS=x$ .

Now

  $\begin{array}{l}\angle RST+\angle STR+\angle TRS=180\\ x+x+70=180\\ 2x=110\\ x=55\end{array}$

  $\angle RST=\angle RTS=55$

All angles of the given triangle are $55$ degree.

So, the given is an isosceles triangle.

Hence, $m\angle RST=55$