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A chapter in one of my calculus books covers using power series to solve differential equations. One example showed the following: cos(nx)*cos(jx) = 1/2(cos(jx-nx) + cos(jx+nx)). I tried working this trig identity on my Prime but couldn't until I came across the "tlin" command.

tlin(cos(nx)*cos(jx)) = +([1/2*cos(jx-nx)1/2*cos(jx+nx)])

"simplify" on the initial result will change it to the customary result: the plus sign between the 2 part of the answer, not preceding (RPN vestige?).