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Prove that `cos 60^(@)=cos^(2)30^(@)-sin^(2)30^(@)`. |
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Answer» `LHS=cos 60^(@)` `=(1)/(2)` `RHS=cos^(2)30^(@)-sin^(2)30^(@)` `=((sqrt(3))/(2))^(2)-((1)/(2))^(2)=(3)/(4)-(1)/(4)=(3-1)/(4)` `=(2)/(4)=(1)/(2)`. `therefore LHS=RHS`. (Proved) |
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