20S pre-cal

Monday, March 13, 2006


Sorry I'm late..Had to scribe for Computer Science tonight as well...=(

Today we started TRIGONOMETRY.

You should already know the 3 laws. If you don't, then here they are:

Sine = opposite/hypotenuse

Cos = adjacent/hypotenuse

Tan = opposite/adjacent

^ If your having trouble looking for the opposite, pick a point to work with. In this case, I picked the right angle. Whatever is across from it is going to be your opposite.
Adjacent is the line that is beside your point.

We began solving some problems with 2 right angle triangles. We had to determine what the length of WX was.

To do this, you must work on the triangle that gives you more information. The triangle xyz is the triangle you should work with first.

First step is to determine the length of the common side. The common side in here is going to be xy.

so far you know that the angle of z is 30°, and Adjacent side s xz = 15cm. Your opposite, which is side xy is still unknown.

You try to fingure out which law would work. The only law that will work here is Tan (opposite/adjacent) since your trying to find out the opposite and you already know the length of the adjacent side.

To do this next step you have to get your calculator. be sure it's set of DEGREES.

1. tan 30° = xy/15
2. (tan 30°)15 = xy/15 (15)
3. (tan 30°) 15 = xy
4. 8.7 = xy

So what I just did in the second step was multiply both sides by 15 to make xy go on it's own. That leaves me with (tan 30°) 15 = xy . On a calculator you would put tan 30 multiplied by 15 and you'll answer will likely be 8.66. Then round to the nearest decimal..


The Homework tonight is

EXERCISE 17 : #1-6 & 12 - 19

and next scribe will be Kaeser.


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