lawrence's holiday blog 3

Converting degrees to rads and rads to degrees.

To convert degrees to rads, its degree X pi/180

Ex. 45 degrees

45 X pi/180= 180/6= pi/4.

Ex. for converting rads to degrees.

pi/6

pi/6 X 180/pi= 180/6 = 30 degrees
remember that the pi's cancel out!!!

I also understood how to get positive and negative coterminal angles.

if its in degrees you substract or add from 360. if its a large negative number and you need to get a positive coterminal angle keep adding it from 360 till you get a positive number.

ex. -1030 degrees
-1030+360+360+360= 50 degrees. (positive)

-1030-360= -1390 degrees. (negative)

if its in radians you just add 2pi or subtract 2pi

Ex. pi/6

pi/6+ 2pi= 13pi/6 (positive)

pi/6- 2pi= -11pi/6 (negative)

The other concept i understood was from 7-4

How to find a reference angle.

1. find the quadrant the angle is in
2. determine if the trig function is positive or negative
3. subtract 180 degrees from the angle until theta is b/w 0 and 90 degrees
4. if it is a trig chart angle plug in. if not leave it or plug in calculator.

ex. cos 225 degrees

its in quad 3
its negative (-cos)
225-180= 45 -cos 45 degrees. (trig chart function)

= -square root 2/2

that is all the concepts that i know the best the others i am decent with so if you need help ask me in class and i will be glad to help.