Let us have a triangle ABC and a point D on BC such that BD=DC=DA. If angle ACB=\(35^\circ\) then how many degrees are in angle ABC?
55 A 35
B 55 70 D 110 35 C
Since AD = DC, then angle ACD = angle DAC = 35 = angle ACB
So angle ADC = 180 - 2(35) = 110° and angle ADB = 70°
But AD = BD so angle DAB = angle ABD .....and by the exterior angle theorem each must measure 55°
So....angle ABC = angle ABD = 55°