Been a while since I ran across something basic that I felt would be good for
this group.

Son and I were discussing polar vs rectilinear coordinates, and we got into cos
and sin, and then I pulled up an animation of cos & sin vs the unit circle, and
then I pulled up an animation of all 6 trigonometric functions to show their
geometric meaning.

Lo and behold, the very next day, I am wanting to diagram out a difference {} of
a wedge-shape from the edge of a box {}.  The axis-aligned length of my adjacent
cathetus is a known length, but when I rotate it around the angle's vertex . . .
what length does the cylinder {} need to be for it to still touch the edge of
the box {} once it's been rotated by angle Theta?  What is the length of that
hypotenuse?

It's the adjacent cathetus length times the secant of Theta, or 1/cos(Theta).
Just realizing this off the top of my head saved me what would have an awful lot
of unnecessary figuring.

Do you have a similar helpful little tip?   Post it here.  :)


- BE

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