Have you learned the cross product yet?
The area of a triangle is given as:
where u and v are vectors whose inital points coincide.
Here, you take .
Take the half the norm and youre' done.
Don't think OC was needed here ...
Hello,
I can't get the correct answer for this and was wondering if anybody could help.
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OA = 5i + 6j - 3k
OB = 3j + 6k
OC = 45i - 30j + 15k
Calculate the area of triangle OAB.
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Thanks for any answers!
Hello !
The area of a triangle ABC is given by
not by the cross product of the vectors from the origin... it would be nonsense
You can use this formula : Heron's formula - Wikipedia, the free encyclopedia, but I doubt it's what you're being expected
Yeah it's triangle OAB. OC wasn't needed for this part of the question (the question has several parts and I included it without thinking). This is the only one I haven't been able to get the right answer for. I tried to find the magnitude of the 3 sides, OA, OB and AB, which I made to be 70^.5, 115^.5 and 45^.5. I put those into the formula for the area of a triangle and came out with about 28, but the answer book says 188.25. So the question is what stupid thing have I done wrong?
Ah ha. Thank you! I wasn't actually wrong (although I wasn't using the best method!). The question/answer was incorrect in my book. It asks for the area of triangle OAB, yet the answer given is the area of triangle OCB. I hadn't thought to work that area out, but you're right.
Thanks for the help guys, seems like the book was wrong!