cos x cos y=1/4 dan sin x sin y= 3/8, sin (x+y)=

cos (x+y ) = cos x cos y - sin x.sin y
= 1/4 -3/8.
= 2/8 - 3/8 = -1/8
sin^2 (x+y) = 1 - cos^2 ( x+y)
sin (x+y) = akar { 1 - cos^2(x+y) }
= akar { 1 - (-1/8)^2}
= akar ( 1 - 1/64)
= akar ( 64/64 - 1/64)
= akar 63/64
= akar (9.7/64)
= 3/8 akar 7