Question

In triangle ABC, AD =DB=DC (see figure). If angle DCB is 60°
and angle ACD is 20°, what is the value of x?​

Answer 1

$\huge{ \underline{ \underline{ \mathscr{ \red{Solution:-}}}}}$

If AD = DB = DC, then the three triangular regions in this figure are all isosceles triangles. Therefore, you can fill in some of the missing angle measurements as shown to the right. Since you know that there are 180° in the large triangle ABC, you can write the following equation:

$x+x+20+20+60+60=180$

$→2x+160=180$

$→x=10$