Question

cana anyone do this please?

Answer 1

The required answer well be 1/2

Answer 2

Cos^2 (1) + cos^2 (2) +cos^2 (3) +.......+ cos^2 (89) + cos^2 (90)
We can write cos^2 x= sin^2 (90-x)
Write this form upto cos^2 (44)

=sin^2 (89) +sin^2 (88)+......+sin^2 (46) +sin^2 (45)+ cos^2 (46) +...............+ cos^2 (88)+cos^2 (89) + cos^2 (90)

We know that sin^2 (x)+cos^2 (x)=1

=1+1+1+....+1 (44 times )+cos^2 (45)+ cos^2 (90)
=44+1/2+0
=89/2