Given vectors:→a=3^i+^j+4^k and →b=^i−^j+^k
→a×→b=∣∣
∣
∣∣^i^j^k3141−11∣∣
∣
∣∣
→a×→b=^i(1×1−(−1)×4)
−^j(3×1−1×4)
+^k(3×(−1)−1×1)
→a×→b=5^i+^j−4^k
Magnitude of →a×→b=√52+12+(−4)2
|→a×→b|=√25+1+16=√42
Area of parallelogram ABCD=|→a×→b|
∴Area of parallelogram ABCD=√42