Hi all,

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)

so that

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?

Many thanks,

Pro