#### Revision Notes

##### What is SOHCAHTOA?

Some American maths teachers claim (jokingly) that Sohcahtoa was a great Native American chieftain and mathematician.  In fact SOHCAHTOA is a mnemonic – ie a way to remember the three important formulas for sin (sine), cos (cosine), and tan (tangent).

In a right-angled triangle, label one angle (NOT the right angle!), and label the sides of the triangles as follows:

(∅  is the Greek letter theta.  ‘O’ stands for opposite, ‘A’ for adjacent, and ‘H’ for hypotenuse.  ‘H’ is always the same, but ‘O’ and ‘A’ depend on which angle we’re calling ∅!)

##### Using SOHCAHTOA

1. Label the triangle.  The angle you know (or want to know) is ‘‘∅’O’ and ‘A’ follow from that.Choose SOH, CAH, or TOA.  The letters of the sides you’re interested in (ie know or want to know) tell you which to choose.
2. To find a side, put and the side you know into the equation from 2., and solve to find the side you don’t know.
3. To find an angle, use the inverse trig functions on your calculator:

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After 24 years teaching A Level Further Maths, Maths whizz Simon focused his attention on tutoring. He’s helped thousands of young people make sense of Maths and now he’s helping you too – aren’t you lucky! He’s even worked as an Edexcel examiner, so knows exactly what they’re looking for.