The second question is really difficult and complicated. I'll tell you why 1 is right first.

Because the graph in Figure 3 is a regular pentagon, each internal angle is 108 degrees, that is, ∠MDQ= 108, and ∠ADC=90, ∠C'DF=∠ADE= 18.

2ab*tan 18=2*ad*de+2ae^2=2*ad*ae+ae^2+ae^2

In the right triangle ADE, AE 2 = de 2-ad 2.

So 2ab * tan18 = 2 * AE * de+AE 2+de 2-ad 2.

Therefore, 2ab * tan 18 = a 2-b 2.