Question

Cos square1°+cos square2°+......…+cos square90°=

Answer 1

Answer:

cos^2[ 1] +cos^2[2]  +cos^2[ 3] +cos^2[4] +...................

cos^2[ 86] +cos^2[87] +cos^2[ 88] +cos^2[89] +cos^2[ 90]

=cos^2[ 1] +cos^2[89]  +cos^2[ 2] +cos^2[88] +cos^2[ 3] +cos^2[87] +.........................cos^2[ 44] +cos^2[46] +cos^2[ 45]+cos^2[90]

=cos^2[ 1] +sin^2[1]  +cos^2[ 2] +sin^2[2] +cos^2[ 3] +sin^2[3] +.........................cos^2[ 44] +sin^2[44] +cos^2[ 45]+cos^2[90]

=1+1+1+........................+1 +[1/2] +0

=44 +1/2 =89/2