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November 7th, 2009, 11:02 PM
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(a)Is triangle ABC a right-angled triangle? Justify your answer.
[Note: A right-angled triangle is a triangle with one 90o internal angle.]
Vector AB is ( 3, 6 , 1)
Vector BC is ( 0 , -7 , -4)
Vector CA is ( -3 , 1 , 3)
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November 8th, 2009, 01:11 AM
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Quote:
Originally Posted by daphnewoon  (a)Is triangle ABC a right-angled triangle? Justify your answer.
[Note: A right-angled triangle is a triangle with one 90o internal angle.]
Vector AB is ( 3, 6 , 1)
Vector BC is ( 0 , -7 , -4)
Vector CA is ( -3 , 1 , 3) | Take the three dot products, see if one of them is 0.
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November 8th, 2009, 01:45 AM
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the x part is zero. thus it is a right-angled triangle? |
November 8th, 2009, 01:48 AM
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No.
Do what I said.
Find  ,  and  , and see if any of these dot products are 0. If so, you have a right angle.
If you do not know anything about dot products (also known as scalar products) I suggest you do a Google search.
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