A triangular metal frame has sides 8 feet, 12 feet, and 16 feet. Find the measure of the largest angle between any two sides of the frame.
The cosine of the largest angle=?

Question

A triangular metal frame has sides 8 feet, 12 feet, and 16 feet. Find the measure of the largest angle between any two sides of the frame. 
The cosine of the largest angle=?

sasogeek · Answer

do you know the cosine rule?

anonymous · Answer

Can you tell me it again? I forgot it

anonymous · Answer

adjacent over hypotenuse

anonymous · Answer

Thanks @Nickv_1 So @sasogeek I just use that?

anonymous · Answer

welcome

sasogeek · Answer

we're not exactly sure if it's a right angled triangle, so we can't also conclude that it's adjacent over hypotenuse.... where is the adjacent, and where is the hypotenuse?

sasogeek · Answer

see, the cosine rule says that if you have a triangle,
|dw:1344729963224:dw|

$\huge cosA=\frac{b^2+c^2-a^2}{2bc} $

we can substitute the values and solve for A (each angle) and see which one is the largest :) then we can find the cosine of that largest angle :)