Помогите доказать тригонометрическре тождество

[latex]sin^2a + cos^2a = 1 sin2a = 2sin(a)cos(a) 4sin^4a + sin^22a = 4sin^2a 4sin^4a+(2sin(a)cos(a))^2 = 4sin^2a 4sin^4(a) + 4sin^2(a)cos^2(a) = 4sin^2a 4sin^2a(sin^2a + cos^2a) = 4sin^2a 4sin^2a = 4sin^2a[/latex]