# Why doesn't Sage do obvious simplifications?

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I wanted Sage to simplify 1/2*(cos(x) + sin(x))*e^x - 1/2*(cos(x) - sin(x))*e^x , which easily comes out to e^x*sin(x), but it simply gave me the original term. Why doesn't Sage combine simple terms, or is there a way to make it do that?
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