Saved Bookmarks
| 1. |
Find the area of a triangle whose vertices are A(i-k), B(2i+j+k),C(j+2k) |
|
Answer» The vector AB = i+j+2k The vector AC = - i+j+3k The area of triangle ∆=(1/2)|AB×AC|= (1/2)|(i+j+2k)×(-i+j+3k)| =(1/2)|-i×i-j×i-2k×i +i×j+j×j+2k×j+3i×k+3j×k+6k×k| =(1/2)|0+k-2j+k+0-2i-3j+3i+0| =(1/2)|i -5j+2k| =(1/2)√(1+25+4) =(1/2)√(30) |
|