sin(A+ B)= sin(A)cos(B)+ cos(A)sin(B).

Set . Of course, there is no "A" such that sin(A)= .5 and cos(A)= 0.25 because [itex]sin^2(A)+ cos^2(A)= 1\ne 0.5^2+ 0.25^2[/tex] but you can both multiply and divide by [itex]\sqrt{0.5^2+ 0.25^2}= \sqrt{5/16}= \sqrt{5}/4[/tex] to get .

Now one problem is that you have and extra ")" with no corresponding "(". Did you mean ? If so then use the fact that first.