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Re: Plotting vs calculating Position
From: Frank Reed
Date: 2015 Jul 30, 13:16 -0700
From: Frank Reed
Date: 2015 Jul 30, 13:16 -0700
Bob, you wrote:
"I have never done sines/consines on a slide rule where any of the angles were larger than 90°."
It's the same as using tables. You employ the basic trig identities involving different quadrants. Suppose you want the cosine of 91° from a table or slide rule that only goes up to 90°. Think about a graph of the function over its range from 0° to 360°. Every quadrant is flipped and/or mirrored from the first quadrant. You can see that cos(91°) is exactly the same as cos(89°) but with a negative sign attached to it. It's also identically equal to -sin(1°). You really only need the first quadrant of the sine function to fill in all the rest by reflection of the argument and/or flipping the sign of the result. Right?
Frank Reed
