I have this fonction? f1=Sin[b??(-m^2/a^2 +(m?(k_? ))/ab)] I want to distribute "b ? " into the square to obtain: f1=Sin?(-b^2?^2m^2/a^2 +b^2?^2(m?(k_? ))/ab) After I suppose??=a/b I will have:f1=Sin?(-?^2m^2/?^2 +?^2(m?(k_? ))/?)

My question is : is there a command in mathematica that can give me this result?

when I have an expression with cosinus or sinus [ex. b²(1/b²t+cos(b²(s/t²+k/t²))] the "expand" command does not expand terms in brackets after cosinus. How can I do to expand this part?

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