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 ∅!)
- 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.
- 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.
- To find an angle, use the inverse trig functions on your calculator: