sin² 45° + cos² 45° - sin² 90°

sin^2 45 + cos^2 45 -sin^2 90
= (sin 45)^2 + (cos 45)^2 - (sin 90)^2
= (1/2 akar2)^2 + (1/2 akar2)^2 -(1)^2
= (1/4 . 2) + (1/4 .2) - 1
= 1/2 + 1/2 -1
= 2/2 - 1
= 1 - 1
= 0

(1√2/2)²+(1√2/2)²-1 = 1/2+1/2-1 = 0