### Solving Trig. Equations

**To Solve Trig. Equations**

**There are two simple rules:**

- Find values which satisfy the equation.
- The domain will always be from [0°,360°], unless stated.

Here are some examples to help you:

ex. sinø = 0.78615 **Solve! **

To solve this question, you first take your (TI 83) calculator and press the (2nd) button, then the (sin-1) button, and type in the number 0.78615. then the calculator will give you a number of 51.83° (round of to two decimal places). Then you need to find out which quadrants have a sin value that is positive (Wednesday's class), which is bquadrantrent 1 quadrantrent 2. So you already hquadrantrent 1 done, it is 51.83° , so to figure out the degree valuequadrantdrent 2 you take 180° ( 180° is the maximum degree value you can have in Quad. 2) and subtract 51.83° from it . The value for Quad. 2 is 1that's°, thats it your done.

sinø = 0.78615

ø= 51.83°

**ør =** 180 - 51.83 = 128.17°

ex. cosø = .43214 ( for (cos) use the same method as above but press the (cos-1) button instead of the (sin-1) button)

**ø **= 64.40°

ø= 360 - 64.40 = 295.6° ( you have to subtract it from 360° , because cosine is positive in quad.1 and quad. 4).

Now try this one on your own. (answer at bottom of page)

2 sinø-1=0 ( hint move the 1 to the other side)

For homework do exercise #9 and ask Mr. Malandrakis for a sheet for review, there is also a quiz tommorow on quad. Equations and trig. equations. So study and Good luck.

Answer to question uptop is ø **= 30° , 150° **

**Tommorow's scribe is Jason.**

**By: Berardino Petrelli (Dino)**

## 1 Comments:

Super Scribe. You went straight forward and right to the point. Adding only information that was totally necessary to the class day. Also your explanation on how to use your calculator is superb. Great Work. I give this scribe post a... B+. The only thing you need is a diagram to explain it even further. ;)

11:55 PM

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