Question

Sin square 5 degree plus Sin square 10 degree plus Sin square 15 degree plus..........Sin square 90 degree

Answer 1

since sin(x) = cos(90-x)

sin^2 0° + sin^2 90° = 1
sin^2 5° + sin^2 85° = 1
...
sin^2 45° + sin^2 45° = 1

Now, you have excluded sin^2 0, but since that's zero anyway. You have 9 pairs, plus a single 45, so the sum is 9.5

Answer 2

sinA=2tanA/2/1 tan.tanA/2