Melody

Not sure what you mean but

$$\\cos\theta=0.63\\
\theta = $inverse cos $ 0.63\\
\theta=cos^{-1}0.63\\\\
$ this is the same as $\\\\
\theta=arc cos 0.63\\
\theta=acos 0.63\\$$

Just use 2nd function  acos

No 

A negative divided by positive is negative.

Also, any number divided by 1 stays the same.

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1 divided by 36 is a tiny POSITIVE number.

A positive divided by a positive is always positive.  

Yes we always must Chris. 

First recognise that 2h+1 cannot equal zero so h cannot equal -1/2

Now multiply both sides by 3(2h+1)

that will get rid of all the fractions and it will  be much easier.  

People sometimes say that 1+1= a window

If you squash that altogether then you and then put a line on top and a line underneath then you have a little french window.  It is a cross inside a square.  I think that is what they mean when they say 1+1= a window.

On the forum calculator inverse tan is replaced with atan  use that button.

x=atan(3/8)

Have a look here.  

I don't know that my mind is made of any material that will rust Rosala.  

My mind is more likely to putrify (go off) I think.

Yes maye some maths might help prevent my brain from putrifying.  LOL