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Qiu senior high school mathematics examination paper analysis! I adopt
1 . sin 150 = sin( 180? -30? )=sin30? = 1/2

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