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Consider the system of linear equations in `x , ya n dz :``""(sin3theta)x-y+z=0(cos2theta)x+4y+3z=0``3x+7y+7z=0`Which of the following can be the value of `theta`for which the system has a non-trivial solution`npi+(-1)^npi/6,AAn in Z``npi+(-1)^npi/3,AAn in Z``npi+(-1)^npi/9,AAn in Z`none of these |
Answer» As given equations has a non-trivial solution, `:. |[sin3theta,-1,1],[cos2theta,4,3],[2,7,7]| = 0` `=>sin3theta(28-21)-cos2theta(-7-7) +2(-3-4) = 0` `=>7sin3theta + 14cos2theta -14 =0` `=>sin3theta +2cos2theta -2 = 0` `=>3sintheta - 4sin^3theta +2- 4sin^2theta -2 =0` `=>-sintheta(4sin^2theta + 4sintheta -3) = 0` `=>sintheta(4sin^2theta + 6sintheta - 2sintheta -3) = 0` `=>sintheta(2sintheta(2sintheta+3) - 1(2sintheta +3)) = 0` `=>sintheta(2sintheta- 1)(2sintheta +3) = 0` `=>sintheta = 0 or sin theta = 1/2 or sin theta = -3/2` `sin theta` can not be less than `-1`, so `sin theta != -3/2`. `:. sintheta = 0 or sin theta = 1/2` `theta = npi or theta = npi+(-1)^n(pi/6).` |
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