beserta rumus dan cara sampai selesai gomawo

cos 1/2a = √(x+1)/2x
cos a = cos (1/2a + 1/2a)
cos a = 2(cos 1/2a)^2 -1
= 2 {√(x+1)/2x }^2 - 1
= 2 (x+1)/2x -1
= (x + 1)/x -1
= ( x + 1 - x )/x
= 1/x
( sin a)^2 = 1 - (cos a)^2
= 1 - 1/x^2
= (x^2 - 1)/x^2
sin a = √(x^2-1)/x^2
sin a = 1/x {√(x^2-1) }