Let vectors 2^i−^j+^k,^i−3^j−5^k and 3^i−4^j−4^k be position vectors of
points A,B and C respectively.
i.e., →OA=2^i−^j+^k,→OB=^i−3^j−5^k and
→OC=3^i−4^j−4^k
Now, vectors →AB,→BC, and →AC represent the sides of ΔABC.
∴→AB=(1−2)^i+(−3+1)^j+(−5−1)^k=−^i−2^j−6^k
→BC=(3−1)^i+(−4+3)^j+(−4+5)^k=2^i−^j+^k
→AC=(2−3)^i+(−1+4)^j+(1+4)^k=−^i+3^j+5^k
|→AB|=√(−1)2+(−2)2+(−6)2=√1+4+36=√41
|→BC|=√22+(−1)2+12=√4+1+1=√6
|→AC|=√(−1)2+32+52=√1+9+25=√35
∴|→BC|2+|→AC|2=6+35=41=|→AB|2
Hence, ΔABC is a right-angled triangle.