If equals to 30 degree verify that cos 2A equals to 1 minus 10 squared

1.	If equals to 30 degree verify that cos 2A equals to 1 minus 10 squared upon 1 + 10 square A
Answer» In the question... There should A=30° in place of equals to 30°........its a typing mistake???? Since A=30°,Cos2A=1-tan^2A/1+tan^2AL.H.S=cos2A=cos2*30°=cos60°=1/2R.H.S=1-tan^A/1+tan^A={1-(1/√3)^2}/{1+(1/√3)^2}=(1-1/3)/(1+1/3)=(2/3)/(4/3)=1/2Hence LHS=RHS

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