Melody

square root of 8 = sqrt(8)

cube root of 8 = sqrt(8,3)

It cannot be simplified (although Badinage has factorized i correctly)

It can be put equal to whatever the problem that you are doing requires. :)

Maybe this will help

I expect it is just too big to display. 

Use atan  it is the same as inverse tan

$$\\4^3=2^x\\\\
(2^2)^3=2^x\\\\
2^6=2^x\\\\so\;\; x=6$$

this was an easy one - if the question is harder then you will need to use logarithms. 

inverse what?

do you mean [2nd] function?

We can not get to every question - there are too many. 

When questions 'fall off' the first page we give them lower priority because we figure you may have already found your answer somewhere else.  If this is not the case we encourage you to draw our attention to your question.  This will almost always work.

Here are instrictions on how it should be done.

cube root of 8

equals 2 because    2*2*2=8

cube root of  343 =    $$\sqrt[3]{343}=7$$

because 7*7*7=343

I hope that helps