In rectangle ABCD below, we have DP = PC and < BAC = 21 degrees. Find the number of degrees in < QDA + < PDC.
Since triangle PDC is an isosceles triangle, and AB is parallel to DC because it is a rectangle, then that means angle DCP is congruent to angle BAC. So angle PCD is 21*. Angle PDC is also 21*.
Angle DAQ is 90 - 21 = 69*. So QDA is 180-90-69 = 21 degrees. Since we are looking for the sum of angles PDC and angle QDA, the answer is 42*.