I have a triangle with
Side A = 2 Side B = 6
Angle c (angle opposite Side C) = 105°
I want to find side C
My first though was to use the SOH CAH TOA rule
In this case we have the adjacent and hypotenuse of angle c so I use CAH (cosθ = A/H)
Because 105° is in the 2nd quadrant it will be -cos
So -cos 105° = 2/C
Therefore C = 2/-cos 105°
I thought this was the correct way to do it because that's all we have been learning in maths.
But in physics we are taught to use C = √(A²+B² - 2ABcosθ) which gives a different answer.
So which do I use/which is more accurate?