Melody

Well it is 

$$\frac{12.5\:miles}{29\:minutes}\\\\
=\frac{12.5}{29}\frac{\:miles}{\:minutes}\\\\
=0.431034482\: miles/minute$$

Now, maybe you want to know what that is in miles/hour?

Well there are 60minutes in an hour and you'll go a lot further in an hour than in a minute so it must be multiply

$$=0.431034482*60\: miles/hour\\\\
\approx\:25.86206897\: miles\: per\: hour\\\\
\approx\:25.9\: miles\: per\: hour \mbox{ correct to 1 dp}$$

$$\begin{array}{rll}
LHS&=&tan\theta (1+cos2\theta)\\\\
&=&\frac{sin\theta}{cos\theta}(1+cos^2\theta -sin^2\theta)\\\\
&=& \frac{sin\theta}{cos\theta}(cos^2\theta+cos^2\theta)\\\\
&=& \frac{sin\theta}{cos\theta}(2cos^2\theta)\\\\
&=& 2sin\theta cos\theta\\\\
&=& sin2\theta\\\\
&=& RHS
\end{array}$$

inverse tan is the same as arc tan

so just press 2nd then atan

There is no fixed way.  Different ways work for different people.  

I never learned them very well.  I just learned to work them out really quickly.

2s are easy. 5s are easy, 10s are really simple.

9s up to are simple - you use your fingers.   do you know that trick?

4s are double 2s

8s are double fours.

3s are a bit tricky but 6s are just double 3s

12s are double 6s

11s are easy. 

so the only REALLY yucky one is 7s

That doesn't matter too much because 7*2 is also a 2*7     7*5 is just 5*7

mmm

So if you find it super difficult to remember them all, just get really good at doubling things and then you can work most of them out really easily.  

You can't.  You can find a if you know b and you can find b if you know a.

but if you don't know either you can't find anything!

Here is the lady that thou seeks.

Alas the beard is newly shaved.

I should not have put that there.  

I know that you didn't mean to offend me.

Thanks Reinout.

Good one reinout!

8/2*100% = 400%

$${\sqrt{{\mathtt{879\,609\,302\,220.8}}}} = {\mathtt{937\,874.886\: \!229\: \!927\: \!792\: \!280\: \!8}}$$

There is no sun, The hour nearly touches 1.  Tis very dark outside even the moon and stars doth hide.

Tonight I praise the dark for the sun is not here to be offended. With the dawn if will change my allegance.  I take not the side of right but the side of victory!