Can This Exponential Identity Be Proven?

[hariyo]

Does anyone know how to prove this?

exp(jAt)+exp(jBt)= 2exp(j(A+B)/2)cos((A-B)/2)

 

[hariyo]

Sorry I think i know by now. Here is the solution.

exp(jAt)+exp(jBt)= 2exp(j(A+B)/2)cos((A-B)/2)

(exp(jAt)+exp(jBt) ) exp(-j(A+B)t/2) exp(+j(A+B)t/2)

(exp(j(A-B)t/2)+exp(-j(A-B)t/2) ) exp(+j(A+B)t/2)

cos((A-B)t/2) 2exp(j(A+B)/2)t