If the position vectors of three points A, B and C are 3 i + j, 5 i +6 j -3 k and 4 j respectively, then show that they form an isosceles triangle.

If the position vectors of three points $\displaystyle \mathrm{A}, \mathrm{B}$ and C are $\displaystyle 3 \hat{\mathrm{i}}+\hat{\mathrm{j}}$, $\displaystyle 5 \hat{\mathrm{i}}+6 \hat{\mathrm{j}}-3 \hat{k}$ and $\displaystyle 4 \hat{\mathrm{j}}$ respectively, then show that they form an isosceles triangle.