it shouldn't be cos(c) but in there should be an angle opposite to the side c in the triangle with sides a,b and c.
I had this equation
x² = a² + b² - c²
these figures fit the equation
a=10, b=5, c=2 giving x=11
121 = 100 + 25 - 4
then it occured to me that the original equation looked very like the Cosine Rule
c² = a² + b² - 2ab Cos(c)
2ab Cos(c) = a² + b² - c²
so combining this with my original equation I would have thought
x² = 2ab Cos(c) which it doesn't ¿ 2 x 10 x 5 x Cos(2) = 99.94......
what did I miss or misunderstand?
Not sure that I understand you though
I'll put the equations together
a² + b² - c² = x²
a² + b² - c² = 2ab.Cos(c)
Surely 2ab.Cos(c) must equal x² for any given a, b & c (10, 5 & 2 in this case)
just had a thought, a triangle can't have sides 10, 5 & 2. Is this perhaps where it falls down?