Wednesday, September 16, 2009

Ramping up to calculus

So a while back I was trying to decide whether to take a stupid liberal-arts course called "Survey of Calculus" since they didn't offer Trig as an evening class. I decided not to, but instead I've set up some appointments with a(n adorable) math tutor to run through the Trig so I can take the placement test at the local university. Hopefully I'll be able to start off with Calculus in the spring, then.

In the meantime, yesterday I (re-)learned:

1) The acronym SOH CAH TOA for sin, cosin, and tangent. Each of these three functions give a ratio of two of the sides of the triangle, for a given angle in degrees. sin(X)=(opposite/hypotenuse), cos(X)=(adjacent/hypotenuse), and tan(X)=(opposite/adjacent). (Interactive "triangle-solver" using these ratios.)

2) If you have the ratio but not the angle, you can reverse-engineer the angle by using the inverse functions sin^(-1) etc. These are applied in the same way that division is the inverse operation to multiplication. So tan^(-1)(3/4)=37 [I'm not looking up the stupid math symbols in html right now] degrees.  (An interactive diagram of a 3:4:5 triangle)

3) Radians are just another unit for measuring angles. Instead of dividing a circle into 360 of the arbitrary units degrees, we divide the circle into 2(pi) of the arbitrary units radians. You convert between them just like you convert between inches and centimeters or any other two units. (This was something I never did properly understand in high school.) (Degree-radian converter, diagram of commonly used angles)

And lastly, I really need to remember that there are 360 degrees in a circle, not 365. Dammit. There was more as well, I'm sure, but that's what I recall without looking at my notes, so I'm gonna go ahead and say that's what I really learned.  We'll see what it looks like after I do some review on my lunch break.

Edit:  The Euler line really is new to me.  I had heard of the Centroid before, but not the Circumcenter or Orthocenter.  Hidden patters are so cool!

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