Bentuk sederhana 2cos(A+π/4).cos(3/4-A)+1

jawab

2 cos (A + π/4)  cos (3/4 π - A) + 1 =

= cos  (A + π/4 + 3/4 π - A) cos (A + π/4 - 3/4 π + A) + 1

= cos (π)  cos (2A - 1/2 π) + 1

= (-1) cos (1/2 π - 2A) + 1

= -  sin (2A) + 1

= 1 - sin 2A

= 1 - 2 sin A cos A