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Объяснение:

1.

sin(π/2-α)=cosα

2.

sin(π-α)=sinα

3.

cos(α+270)=cos(α+180+90)=

=cos(180+90+α)= -cos(90+α)=

= -(-sinα)=sinα

4.

cos(α-180)=cos(-180+α)=cos(-(180-α)=

=cos(180-α)= -cosα

5.

cos²(3π-α)=(-cosα)²=cos²α

6.

sin(3π/2+α)=sin(π+π/2+α)=

= -sin(π/2+α)= -cosα