Cos² (2 п-t) + cos² (2 п+t)

1. cos^2 (/pi+t) + cos^2 (/pi-t) =

=cos (/pi+t) * cos (/pi+t) + cos (/pi-t) * cos (/pi-t) =

= (-cos (t)) ^2 + (-cos (t)) ^2=2cos^2 (t)

2. cos (2/pi-t) - sin (3/pi/2+t) = 1

cost+cost=1

2cost=1

cost=1/2; t=/pi/3

3. sin (2/pi-t) - cos (3/pi+t) - 1=0

-sint-cos (/pi+t) = - 1

-sint+cost=-1

sint-cost=1

sint [-1; 1]; cos[-1; 1] = > sint=1: cost=0

t=/pi/2