2cos² (45°+4a) + sin8a=1

2cos² (45+4a) + sin8a = 1

cos²x = (1+cos2x) / 2 - формула

2cos² (45+4a) + sin8a = 1

2 (1+cos2 (45+4a)) / 2 + sin8a = 1

1+cos2 (45+4a) + sin8a = 1

1 + cos (90+8a) + sin8a = 1

cos (90+a) = - sina формула

1 + cos (90+8a) + sin8a = 1

1-sin8a + sin8a = 1

1 = 1