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**[SOLVED] triangle problem using vectors**

Hi!

question: Two sides of a triangle are formed by vectors i - 4j-k and -2i - j+k. The area is ?

A=1/2bh so I know to multiply the two vectors as such 1/2(vector1 x vector2) But what do I substitute foe i, j and k? Its not given in the problem.

so far...

1/2(-2i^2-ij+ik+8ji+4j^2-4jk+2ki+kj-k^2)

so what do I substitute foe i, j and k?

Dx