State whether a triangle formed with sides having the lengths named is acute, right, or obtuse.

3,4,6

9,12,15

5,6,7

How the heck can I solve this? Please explain!

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- May 6th 2007, 12:54 PMwhytechocolate01Triangles!!! acute, obtuse, or right???
State whether a triangle formed with sides having the lengths named is acute, right, or obtuse.

3,4,6

9,12,15

5,6,7

How the heck can I solve this? Please explain! - May 6th 2007, 01:08 PMThePerfectHacker
Use the law of cosines or Heron's formula.

Let us use law of cosines, because you have a better chance of hearing of it.

#1] Let a=3 b=4 and c=6.

Then, we can find all the angles of this triangle.

Say angle A.

a^2=b^2+c^2-2bc*cos(A)

9=16+36-48*cos(A)

You can solve for cos(A) and then take arccos to get the angle.

Now do that will all angles.

Then you can determine whether the triangle if acute or not.