JEE Adv. 2013: $K\left[ {\frac{x}{{{{({x^2} + {y^2})}^{3/2}}}}\hat i + \frac{y}{{{{({x^2} + {y^2})}^{3/2}}}}\hat j} \right]$
Solution
The equation of the circle is x2+y2=a2
Hence, (D)
If the sum of the coefficients in the expansion of $(x+y)^n$ is 4096, then the greatest coefficient in the expansion is _ _ _ _ . Solution $C_0 + C_1 + C_2 + C_3 + ......................... + C_n =4096 $ $\therefore 2^n = 4096 =2^{12} $ $\Rightarrow n = 12 $ Greatest coefficient = ${}^{12}{C_6} = 924$