This past week in advanced math we covered most of chapter seven. At first it seemed overwhelming, but once you look at everything just one step at a time I really isn’t that complicated.
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 absolute value of theta is between 0 and 90 degrees.
4. If it is a trig chart angle, plug it in. If not, leave it or plug it in the calculator.
***Hint-- evaluate means the answer is a number unless otherwise specified.***
**If asked for radiants-
0 degrees= 0
30 degrees = pi/6
45 degrees = pi/4
60 degrees = pi/3
90 degrees = pi/2**
Example One------
Sin 405
First, you must decide what quadrant on the graph 405 is in. Since it is bigger than 360 you must go around the grid once and a little more.
Once you have done that, you see sin is positive since it is in the first quadrant.
+ Sin 405
Next, you must subtract 405 from 180
180-405= -225
Then take the absolute value of -255
I-225I
Which equals 225
Since 225 is larger than 90 you must subtract from 180 again.
180-225= -45
Take the absolute value again
I-45I
Which gives you 45
Since 45 is between 0 and 90 you don’t have to do anything else unless it asks for radiants
If they ask for radiants, look back at the chart above and you can see that 45 = pi/4
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