Introduction

Trigonometric Functions (on Angles)	Trigonometric Ratios (of Lengths)	Mnemonics
$\sin \theta$	$$\frac{{{\rm{Opposite}}}}{{{\rm{Hypotenuse}}}}$$	SOH
$\cos \theta$	$$\frac{{{\rm{Adjacent}}}}{{{\rm{Hypotenuse}}}}$$	CAH
$\tan \theta$	$$\frac{{{\rm{Opposite}}}}{{{\rm{Adjacent}}}}$$	TOA

Download the Notes (Mnemonics): http://db.tt/DaO9aP6Z


In the past, when calculators were not easily available, trigonometric functions/ratios were obtained from a "Trigonometric Table", as shown below.

Uses of Trigonometry




History of Trigonometry