It is known that, as shown in the figure, P is the interior point of the square ABCD, ∠ pad = ∠ PDA = 15 °. It is proved that △ PBC is an equilateral triangle

It is known that, as shown in the figure, P is the interior point of the square ABCD, ∠ pad = ∠ PDA = 15 °. It is proved that △ PBC is an equilateral triangle

It is proved that: ∵ square ABCD, ∵ AB = CD, ∵ bad = ∵ CDA = 90 °, ∵ pad = ∵ PDA = 15 °, ∵ PA = PD, ∵ PAB = ∵ PDC = 75 °, congruence of △ DGC and △ ADP is made in the square, ∵ DP = DG, ∵ ADP = ∵ GDC = ∵ DAP = ∵ DCG = 15 °, ∵ PDG = 90 ° - 15 ° - 15 ° = 60 °, ∵ PDG is equilateral triangle (an isosceles triangle with an angle equal to 60 degrees is equilateral triangle),