6. is an isosceles triangle in which . Side BA is produced to D such that (see Fig.). Show that is a right angle.
Consider ABC,
It is given that AB = AC
So, (Since angles opposite to the equal sides are equal.)
Similarly in ACD,
We have AD = AB
and
So,
or ...........................(i)
And in ADC,
..............................(ii)
Adding (i) and (ii), we get :
or
and