AIEEE 2006 (Offline)Question 1
The values of $a$, for which the points $A,B,C$ with position vectors $2\hat i-\hat j+\hat k$, $\hat i-3\hat j-5\hat k$ and $a\hat i-3\hat j+\hat k$ respectively are the vertices of a right angled triangle with $C=\frac\pi2$ are :
Vector Algebra
Solution
$\overrightarrow{CA}=(2-a,2,0)$, $\overrightarrow{CB}=(1-a,0,-6)$. $\overrightarrow{CA}\cdot\overrightarrow{CB}=(2-a)(1-a)=0\Rightarrow a=1,2$.