99 Percentile Qs Bank for JEE MainMathematicsThree Dimensional Geometry
3 i -2 j - k ,-2 i - j +3 k and - i +3 j -2 k are the position vectors of the vertices A, B and C of a A B C respectively. If H is its orthocenter, then HA + HB + HC =
Options
- A2 SA
- B0
- C2 AB
- Di + j + k
Correct answer
B. 0
Step-by-step solution
Let H( i + j + k ) be the orthocentre of the ABC . Since A H B C =0 A H B C +4 -5 =0 ...(1) aligned & Since B H A C B H A C =0 & 5 - -4 =0 ...(2) aligned Since C H A B Hence C H A B =0 5 - -4 =0...(3) Solving equation (1), (2) & (3) we get = = =0 Hence orthocentre is H (0,0,0) aligned & Hence H A + H B + H C =(3 i -2 j - k )+(-2 i - j +3 k ) & +(- i +3 j -2 k ) & = 0 aligned