срочно!!!!!!!!!!!!!!!!!!!!!!!

1) cos 2a + sinˇ2 a = cos ˇ2a sinˇ2 a + sinˇ2a = cosˇ2a
2)(sin2a(/2.cosa = (2.sina cosa)/2.cosa = sina
3)sina/(2.sinˇ2a/2 = sin (2.a/2)/(2.sinˇ2a/2 = 2. sin(a/2).cos(a/2) /(2.sinˇ2a/2 = cos(a/2)/sin(a/2) = cotg (a/2)
4)sin 100/2.cos 50 = sin(2.50)/2.cos50 = (2.sin50.cos50)/2.cos50 = sin50

а можно з?

sina/(2.sinˇ2a/2)= (sin 2.a/2)/2.sinˇ2a/2)=(2.sina/2.cosa/2)/2.sinˇaa/2 =

cos(a/2)/sin(a/2) = cotg (a/2)