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The number of possible value of `theta` lies in `(0,pi)`, such that system of equation `x+3y+7z=0`, `-x+4y+7z=0`, `xsin3theta+ycos2theta+2z=0` has non trivial solution is/are equal to (a) 2 (b) 3 (c) 5 (d) 4A. oneB. twoC. threeD. none of these |
Answer» Correct Answer - D The given system of equations has a non-trivial solution `{:abs((1,3,7),(-1,4,7),(sin3theta,cos2theta,2))=0:}` `rArr{:abs((0,7,14),(-1,4,7),(sin3theta,cos2theta,2))=0:}` [Applying `R_1toR_1+R_2`] `rArr -7(-2-7sin3theta)+14(-cos2theta-4sin3theta)=0` `rArr 2+7sin3theta-2cos2theta-8sin3theta=0` `rArr 2cos2theta +sin3theta=2` `rArr 2(1-2sin^2theta)+3sintheta-4sin^3theta=0` `rArr 4sin^3theta+4sin^2theta-3sintheta=0` `rArr sintheta(4sin^2theta+4sintheta-3)=0` `rArr sintheta (2sintheta-1)(2sintheta+3)=0` `rArr sintheta =0or, sintheta=1/2` `rArr theta=0,pi,pi/6,(5pi)/6` |
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