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IloveCharlie
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=?
do you know the cosine rule?
Can you tell me it again? I forgot it
adjacent over hypotenuse
Thanks @Nickv_1 So @sasogeek I just use that?
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?
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 :)
let's say for example using this triangle, |dw:1344730155989:dw| \(\huge cosA=\frac{16^2+8^2-12^2}{2(16*8)} \) we can solve for A by taking the cos inverse of the value on the right side of the equation.
"on the right side of the equation"?
yeah, every equation has 2 sides :) left side = right side | | | | \(cosA \ \ \ \ = \frac{16^2+8^2-12^2}{2(16*8)} \)
so to find A, we find the cos inverse of the right side, like this... \(\huge A = cos^{-1}(\frac{16^2+8^2-12^2}{2(16*8)}) \)
I'm trying to solve. Just a sec
I keep getting error when trying to solve using my TI83
hmm, let's see what i get..just a sec
angle A = 79.193 degrees :)
Thank you! So the final answer is 79.193?
no, you'll have to check the other angles to be sure which one is the largest :)
Oh o.k. So I use the same formula?
yeah :) i'll do it and tell you what i got, in the mean time, do it yourself and let me know what you got too :)
sorry i made a mistake somewhere, A=46.567 B=104.478 C=28.955
Oh :/ Was it the formula or a mistake in the arithmetic?
i just miscalculated, the formula is correct though, the last answers i put up are right... did u get the same thing?
Yes, I used the formula :) So obviously B is the largest angle
:) so u got the largest angle, what are u supposed to do with it?
Take cosine. So just a sec... -.2500?
yay! :) our work is done here :)
And I couldn't have done it without you! Thank you so much I really appreciate it :)
anytime :) you're welcome :)