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If sin A + sin 2A = x and cos A + cos 2A = y, then `(x^(2)+y^(2)) (x^(2)+y^(2)-1)=`A. 2yB. yC. 3yD. none of these |
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Answer» Correct Answer - A Squaring and adding, we get `x^(2)+y^(2)=1+1+2 cos (2A-A)` `therefore (x^(2)+y^(2)-2)/(2)=cos A` ….(1) Also `cos A + 2 cos^(2)A-1=y` or `(cos A+1)(2cos A-1)=y` Put value of cos A from (1) and and get the answer. |
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