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## Homework Statement

Hi

Find the (finite,ultimate,definitive,peremptory,eventua,conclusive) sum:

[tex]a) cos^2x+cos^22x+...+cos^2nx ; b) sin^2x+sin^22x+...+sin^2nx [/tex]

## Homework Equations

z=A+Bi

## The Attempt at a Solution

[tex]A=cos^2x+cos^22x+...+cos^2nx[/tex]

[tex]B=sin^2x+sin^22x+...+sin^2nx[/tex]

[tex]z=cos^2x+cos^22x+...+cos^2nx+i(sin^2x+sin^22x+...+sin^2nx)=(cos^2x+isin^2x)+(cos^22x+isin^22x)+...+(cos^2nx+isin^2nx)=(cos^2x+isin^2x)+[/tex]

[tex](cos^2x+isin^2x)^2+...+(cos^2x+isin^2x)^n[/tex]

How will I continue?

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