Isolating 2abCos(c) on one side of the equation and using the given values of a, b and c we can find the answer to this question as shown below:
[tex] a^{2} + b^{2} -2ab*cos(C)=c^{2} \\ \\
2ab *cos(C)= a^{2} + b^{2} - c^{2} \\ \\
2ab *cos(C)=2^{2} + 2^{2}- 1^{2} \\ \\
2ab*cos(C) = 7 [/tex]
