2. In the range of 0 to 2π, the angle 2π/3 is the same as the terminal edge of the angle -4π/3.

∵-4π/3+2π=2π/3

3. if cos α >; 0，sinα& lt； 0, and the terminal edge of angle α is in the fourth quadrant.

cosα& gt； 0 = = >； α lies in 1, 4 (positive direction of X axis)

sinα& lt； 0 = = >； α is in 3,4 (negative Y axis)

Male Quadrant 4 * * *

4.√( 1-sin？ 440 )=√cos？ 440? =|cos440？ |=|cos(360？ +80? )|=cos80？

5. Simplify SIN (180+2α)/1+cos2α× [cos2α/cos (90+α)].

=sin2α/(2cos？ α) ×cos？ α/(-sinα)= 2 sinαcosα/[2(-sinα)]=-cosα

D.- Kossa