Question 954939
Law Of Cosines, {{{c^2+b^2-2cb*cos(A)=a^2}}};


Symmetric Property and substitute given values, {{{a^2=90^2+45^2-2*90*45*cos(30)}}};


Evaluate or compute, and find square root of {{{a^2}}}.


{{{a=sqrt(90^2+45^2-2*90*45*cos(30))}}}





Study the form of the formula carefully, and you should be able to make two other equations.


One of them,  {{{a^2+b^2-2ab*cos(C)=c^2}}}.