document.write( "Question 1014481: there are 12 points a1,a2,...a12 in a plane,no 3 on the same line,no 3 on the same line.how many triangles that contain a1 as a vertex determined? \n" ); document.write( "

Algebra.Com's Answer #631243 by robertb(5830) $\"\"$ $\"About$

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With the point a1 excluded, two points have to be selected from the remaining eleven points to form a triangle. The number of ways of doing this is C(11, 2) = 55. Therefore there are 55 different triangles formed. \n" ); document.write( "

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