## Archive for the ‘Mnemonics’ Category

### Hyperbolic Mnemonic

Friday, 11 October 2013

If you have problems remembering which is which with sinh and cosh, or their graphs, or which way around their definitions are:

$\sinh x = \dfrac{\mathrm{e}^x - \mathrm{e}^{-x}}{2}$

$\cosh x = \dfrac{\mathrm{e}^x + \mathrm{e}^{-x}}{2}$

then it might help if you notice that the graph of sinh is somewhat S-shaped (though backwards), and cosh is C-shaped (though open upwards).

[Well, unless you’re Russian, where the Cyrillic letter Es (‘С’) corresponds to our ‘S’; that might throw a graphemic spanner in the works.]

### Learning the Multiplication Tables

Tuesday, 21 December 2010

In a previous post, I tried to show that learning the multiplication tables need not be daunting for children (or even adults). Here are a few odd methods and techniques that might also help.

### Colour Mixing

Sunday, 26 April 2009

There seems to be some confusion about what the primary and secondary colours are. Well, it depends.

### Dimensional Analysis of the Kinematic Equations

Sunday, 26 April 2009

To help to remember the kinematic equations, it may be useful to know a little dimensional analysis.

### Planetary Mnemonic

Tuesday, 21 April 2009

Here’s something I noticed that might help people to remember the order of some of the planets – mainly the gas giants.

Beyond Mars are:

• Jupiter
• Saturn
• Uranus
• Neptune

notice the initial letters in the order SUN away from the Sun.

### Dimensional Analysis of Statistical Formulae

Monday, 20 April 2009

Dimensional analysis (also used in Physics) can be used to check statistical formulae.

### Trigonometric Mnemonic

Wednesday, 8 April 2009

At school we had a saying with which to remember the trigonometric forms:

• $\sin(\vartheta) = O/H$
• $\cos(\vartheta) = A/H$, and
• $\tan(\vartheta) = O/A$

in a right-angled triangle, where

• $\vartheta$ is one of the other angles
• $O$ is the short side opposite the angle
• $A$ is the short side adjacent to the angle, and
• $H$ is the hypotenuse (the long side).

The saying was

Some Old Horses
Can Always Hear
Their Owners Approach.

### Possessive Apostrophes

Tuesday, 7 April 2009

There’s a very easy rule for using apostrophes to indicate possession.