n the figure, BA = AD = DC and point D is on segment BC. The measure of angle ACD is 25 degrees. What is the measure of angle ABC?
Since AD = DC, angle(DAC) = angle(DCA) = 25o.
This means that angle(ADC) = 180o - 25o - 25o = 130o.
So, angle(BDA) = 180o - 130o = 50o.
Since BA = AD, angle(ABC) = 50o.
Notice that angle(ABD) is twice as large as angle(ACD). Will this always be true?