Prove: Area of Triangle Between Vector a & b & Red Line = 1/2 |a x b|

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The area of the triangle formed by vectors a and b, along with the red line, is definitively established as 1/2 |a x b|. The formula for the area of a triangle, A = 1/2 * base * height, applies here, with vector b serving as the base. The height of the triangle is determined by the sine of the angle θ between vectors a and b, specifically A = 1/2 * |b| * |a| * sin(θ). This relationship confirms the area calculation using the cross product of the vectors.

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1. Show that the area of the triangle contained between vector a and vector b and the red line is 1/2 |a x b|

So far i have that bcosO would equal a ...and that 1/2bh should be the area... but I am stuck. can somebody help me prove?
 
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[itex]b\cos\theta=a[/itex] is not correct. Assuming vector b forms the base of the triangle, [itex]A=1/2bh[/itex] is the correct equation for the area. So what is the height of the triangle? (Hint: it involves only a and theta).
 

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