After concluding plane geometry we took trigonometry. The teacher had chosen an ugly pink-and-black text from New York State. No less than 3 inches thick, it wa

After concluding plane geometry we took trigonometry. The teacher had chosen an ugly pink-and-black text from New York State. No less than 3 inches thick, it was chock full of trigonometric formulae for us to memorize. But on day 1 she put the following on the blackboard: Indian Chief SOHCATOA: S=O/H C=A/H T=O/A where S, C, T, O, A, H are respectively, sin, cos, tangent, opposite, adjacent, and hypotenuse. The mnemonic stuck immediately. Surprised, I asked if all the formulae in the 3-inch text were in terms of those formulae, to which she replied affirmatively. I immediately realized there was little need to study trig whatsoever, since any of the complex formulas could be reduced to ratios using the SOCAHTOA principle. I barely cracked the text that semester. She disapproved somewhat of my methods but accepted them. My classmates wasted hours memorizing formulas.