| Proof |
Visit
mathsnet for notes
and interactive explanations. |
| The
cosine rule |
Check
out the proof at this Japanese
site. |
| The
sine rule |
The
site
in Japan also has a proof for this rule. |
| The
sum of an arithmetic progression/series |
Practise
the proof with nrich. |
| The
sum of a geometric
progression/series |
Check if you know this proof at nrich. |