Question

In the figure,prove that d=a+b+c​

Answer 1

Answer:

since d is an inner vertex angle so a+b+c = d

Answer 2

Answer:

join BD and expand upor E

then,external angle ADE of the triangle ABD

=angle DAB+angle ABD

again,external angle CDE of the triangle BDC

= angle DBC+angleBCD

so,

ADE+CDE=DAB+ABD+DBC+BCD

ADC=DAB+ABC+BCD

d=a+b+c