Q.

The vertices B and C of a triangle ABC lie on the line x1=1-y-2=z-23. The coordinates of A and B are (1,6,3) and (4,9,α) respectively and C is at a distance of 10 units from B. The area (in sq. units) of ABC is:                 [2026]

1 513  
2 1013  
3 2013  
4 1513  

Ans.

(1)

41=9-12=α-23α=14

AD·(i^+2j^+3k^)=0

(λ-1)i^+(2λ-5)j^+(3λ-1)k^=AD

λ-1+4λ-10+9λ-3=0

14λ=14λ=1

D=(1,3,5)

AD=32+22=13

Ar(ABC)=12×13×10=513