The sum of the angles is 180 degrees. How do you find the other two angles if the third angle is 55 degrees??

2 Answers

Jasmine JOgirl Profile
Jasmine JOgirl answered

So there are three ways to do this. If you have 2 sides of the triangle you can use SOH-CAH-TOA to find the other angles. S= sin, O= opposite side of the angle, H= hypotenuse. The hypotenuse is the longest side of the triangle.  C= cos, A= adjacent, adjacent means the side next to the angle, H= hypotenuse. T= tangent, O= opposite, A= adjacent. You could take 180 and subtract 55 to figure out what you have left then you can figure out  what you need to do next. The other way that I can think of is to use the law of sines which is sin A/ A, Sin B/B, Sin C/C. You can use this to equal Sin A/A = Sin C/ C or any combination as long as you don't mix them together like Sin A/ C because it just wouldn't work. Sin= the angle and A,B, and C equals the sides so if you say Sin A you are saying angle A. This can work if you have two sides. You would set it up as Sin 55/what ever side is A which is = to let's say Sin C/ whatever side is C. Then you can cross multiply to say whatever side is C sin 55/whatever side is A = Sin C then you use your calculator to Sin-1 the answer to get what the angle of C is. Then add them together and subtract from 180 for the last angle.

Claire MotherofPetey Profile

You can't do it unless you know another angle or the two sides adjoining 55*.

You could do this:  180 - 55 = 125. So the sum of the other 2 angles is 125.      

Call one of those A & the other B.      

A + B = 180 --> B = 180 - A                            

The other 2 angles are A and 180 - A.

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