View entire discussion
The trig ratios are essentially names that have been assigned to the common ratios of similar triangles (those whose angles have the same measures, like 30-60- 90 degrees, or any other combination whose total is 180 degrees). There is a great fictional story written about Sohcahtoa. Sohcahtoa is one way students can remember how to find the ratios. Soh stands for Sine is Opposite over Hypotenuse cah = Cosine is Adjacent over Hypotenuse toa = Tangent is Opposite over Adjacent. I prefer this mnemonic to Oscar Had A Heap Of Apples because although the oh..ah..oa is there, the students forget which one goes with which trig function. Opposite refers to the side opposite the angle you are working with. If I had a triangle A B C then AC would be the hypotenuse because it is opposite the right angle of B. The sin A = BC/AC since side BC is opposite angle A. cos A = AB/AC since AB is the side adjacent (near/connected to) angle A. Hope this gets you started!
Math Forum Home || The Math Library || Quick Reference || Math Forum Search