Question

TRUE or FALSE!

The law of cosines reduces to the Pythagorean theorem when the triangle is right.

**my answer: FALSE!
is that right? @terenzreignz :)

Answer 1

What's the law of cosines?

\[\Large c^2 = a^2+b^2 -2ab \ \cos(C)\]

Answer 2

So, if it's a right angle, then we have C = 90 degrees...
\[\Large c^2 = a^2+b^2-2ab \ \cos(90^o)\]

Answer 3

yup haha thats it :P

Answer 4

What's cos(90) = ?

Answer 5

=0 ?

Answer 6

That's right, so this part just cancels out...
\[\Large c^2 = a^2 + b^2 \cancel{-2ab \ \cos(90^o)}\]

Leaving you with...?

Answer 7

pythagorean theorem! :) so this is actually TRUE! ahh i see :)

Answer 8

haha

Answer 9

pythagorean theorem! :) so this is actually TRUE! ahh i see :)