Question 515469
<pre>
cos(x) + sin(x) = {{{sin(2x)/2}}}

Sorry, but this isn't true!  Did you copy it wrong?

To disprove it simply use x=0

cos(0) + sin(0) = {{{sin(2*0)/2}}}

          1 + 0 = {{{sin(0)/2}}}

              1 = {{{0/2}}}

              1 = 0

False!

Edwin<pre>