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Solve the equation `sin^(4)x + cos^(4)x =7/2 sinx.cosx.` |
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Answer» `sin^(4)x+cos^(4)x=7/2sinx.cosx rArr (sin^(2)x +cos^(2)x)^(2) =7/2sinx.cosx` `rArr 1-1/2(sin2x)^(2)=7/4(sin2x) rArr 2sin^(2)2x+7sin2x-4=0` `rArr (2sin2x-1)(sin2x+4) =0 rArr sin2x =1/2` or `sin2x = -4` (Which is not possible) `rArr 2x = npi+(-1)^(n)pi/6 , n in I` i.e, `x=(npi)/(2)+(-1)^(n)pi/12, n in I` Ans. |
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