If your using this as the Pythagorean theorem then this is correct. You can use
a2+b2=c2 to find the missing side on a right triangle only. However, in the law of cosines, it is c2=a2+b2-2ab cos C. In a right triangle, the cosine of C is the angle opposite the hypotenuse which is 90o. The cosing of 90o is 0 so you would be left with a2+b2=c2.
If I have this correct you are asking x^2 + 10^2 = 12^2 Then x=6.633249507108
104
3
89
pythagoras
b = 14324.80366
b= 10
X = √63
2 squared plus 2 x 3 = 10, 7 squared plus 7 x 2 = 63, 6 squared plus 6 x 5 = 66,8 squared plus 8 x 4 = 96 so 9 squared plus 9 x 7 = 81 + 63 = 144.
16
the person who came up with that is pythagoris, and it is called the pythagrian theorem.
This is the common form of the Pythagorean Theorem. It describes the relationship between the two legs of a right triangle and the hypotenuse.