1). Diketahui cos A = ().6, jika sudut A di kuadran I maka sin A = .. 2). Jika f(x) = x - 2, maka f(2x) + 2f(x) adalah .. 3). Nilai dari cos 1/6π x sini 2/3π -

3.
cos 1/6 π * sin 2/3 π - sec 0
= cos (1/6 *180) * sin (2/3 * 180) - 1/cos 0
= cos 30 * sin 120 - 1/1
= 1/2 √3 * sin 60 - 1
= 1/2 √3 * 1/2 √3 - 1
= 1/4 * 3 - 1
= 3/4 - 1
= -1/4

4.
(sin A + cos A)(sin A - cos A)
= sin^2 A - sin A cos A +sin A cos A - cos^2 A
= sin^2 A - cos^2 A
= 1 - cos^2 A - cos^2 A
= 1 - 2 cos^2 A