Question 1115369
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What do you mean "solve"?<br>
There is no equation; there is nothing to solve.<br>
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Again, "simplify" is not specific.  In this example, there is an easy first step to simplify the expression; then there is another less trivial way to simplify the expression further.  But we don't know where we are supposed to stop in the simplification process....<br>
{{{sin(x)^4-cos(x)^4)}}}
{{{(sin(x)^2+cos(x)^2)*(sin(x)^2-cos(x)^2)}}}
{{{(1)(sin(x)^2-cos(x)^2)}}}
{{{(sin(x)^2-cos(x)^2)}}}<br>
The original expression has been simplified; but it can be simplified further.  Do you see how?