=−1 ⇒h=18,k=−2 Coordinate of B is (18,−3,0) and C(−4,−2,−1), (AB)2=(18−1)2+(−3−2)2+(0−3)2 =(17)2+52+32 =289+25+9 =323 (BC)2=(−4−18)2+(−2+3)2+(−1−0)2 =484+1+1=486 (CA)2=(−4−1)2+(−2−2)2+(−1−3)2 =25+16+16=57 (AB)2+(CA)2=323+57 =380<(BC)2 ∴△ABC is an obtuse angled triangle.