b)Find the area of the triangle PQR.

Solution:

a) Let a and b be the vectors defined below. Then the orthogonal vector is the cross product a x b.

Therefore, the vector orthogonal to the plane is

b) = area of parallelogram formed by vectors a and b.

= area of the triangle formed by vectors a, b and a + b

Therefore, the area of the triangle is .

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by:sh
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