JEE Main & Advanced Sample Paper JEE Main - Mock Test - 37

  • question_answer
    If \[A\left( cos\alpha ,\text{ }sin\alpha  \right),B\left( sin\alpha ,-cos\alpha  \right),C\left( 1,2 \right)\] are the vertices of a \[\Delta ABC\], then as \[\alpha \] varies the locus of its centroid is -

    A) \[{{x}^{2}}+{{y}^{2}}-2x-4y+1=0\]

    B) \[{{x}^{2}}+{{y}^{2}}-2x-4y+3=0\]

    C) \[3\left( {{x}^{2}}+{{y}^{2}} \right)-2x-4y+1=0\]

    D)  None of these

    Correct Answer: C

    Solution :

    [c] So let centroid is (h, k) \[h=\frac{cos\alpha +sin\alpha +1}{3},K=\frac{sin\alpha -cos\alpha +2}{3}\] \[\Rightarrow cos\alpha +sin\alpha =3h-1\]           .....(i) \[\Rightarrow sin\alpha -cos\alpha =3k-2\]              ?..(ii) Squaring and adding \[2={{\left( 3h-1 \right)}^{2}}+{{\left( 3k-2 \right)}^{2}}\] locus \[{{\left( 3x-1 \right)}^{2}}+{{\left( 3y-2 \right)}^{2}}=2\]


You need to login to perform this action.
You will be redirected in 3 sec spinner