Question

If angle d=130 and angle c=60, what is angle a?

Answer 1

The sum of all internal angles of a triangle is 180°, therefore

`a+b+c=180`

Also, we know that

`b+d=180`

We have the value of d then we can find b using the second equation

`\begin{gathered} b+130=180 \\ \\ b=180-130 \\ \\ b=50 \end{gathered}`

Therefore

`\begin{gathered} a+50+60=180 \\ \\ a=180-50-60 \\ \\ a=180-110 \\ \\ a=70 \end{gathered}`

The value of a is 70°