Answer :
Left side:
1-sin²(x) = cos²(x)
1-sin²(x) / cos(x) = cos²(x) / cos(x) = cos(x)
Right side:
sin(2x) = 2 sin(x) cos(x)
sin(2x) / 2 sin(x) = 2 sin(x) cos(x) / 2 sin(x) = cos x
1-sin²(x) = cos²(x)
1-sin²(x) / cos(x) = cos²(x) / cos(x) = cos(x)
Right side:
sin(2x) = 2 sin(x) cos(x)
sin(2x) / 2 sin(x) = 2 sin(x) cos(x) / 2 sin(x) = cos x