SOLUTION: Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm, and 8.0 cm.

Algebra ->  Trigonometry-basics -> SOLUTION: Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm, and 8.0 cm.      Log On


   



Question 1101467: Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm, and 8.0 cm.
Found 3 solutions by Alan3354, stanbon, ikleyn:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm, and 8.0 cm.
------------
It's opposite the longest side.
Use the Cosine Law.

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm, and 8.0 cm.
------
The angle opposite the largest side is the largest angle.
----
a^2 = b^2 + c^2 - 2bc*Cos(A)
------
Cos(A) = [b^2+c^2-a^2]/(2bc)
-----------------
Cos(A) = [6^2+7^2-8^2]/(2*6*7) = -0.9167
----
A = arccos(-0.9167) = 156.44 degrees
-------------------
Cheers,
Stan H.
-------------


Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.
Find the largest angle in a triangle with sides 6.0 cm, 7.0 cm, and 8.0 cm.
~~~~~~~~~~~~~

The angle opposite the largest side is the largest angle.


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


Cos(A) = [b^2+c^2-a^2]/(2bc)


Cos(A) = (6^2+7^2-8^2)/(2*6*7) = 1%2F4.


A = arccos(1/4) =   75.56 degrees (approximately).