answer: 2 ... but how???
cos^2(20°) + cos^2(52°) + cos^2(38°) + cos^2(70°)
thanks to those who are helping everyone pass their class! your efforts are appreciated greatly :)
Note cos (20°) = sin (70”)
And cos(52°) = sin (38°)
So.....we have
sin^2(70°) + sin^2(38°) + cos^2(38°) + cos^2(70°) rearrange as
[sin^2 (70°) + cos^2(70°)] + [ sin^2(38°) + cos^2(38°) ] =
1 + 1 = 2