Question

in the adjoining figure, DA=DB=DC, show that angle ACB=90 degree

Answer 1

In triangle CDB
DB=DC
<2=<1. .......(1)
In triangle ADC
DA=DC
<6=<5. .......(2)
In triangle ABC
<1+<2+<5+<6=180
from equation 1 and 2
<2+<2+<5+<5=180
2(<2+<5)=180
(2+<5)=90