Evaluate each expression without using a calculator, and write your answers in radians.

1. sin^-1 (sqrt(3)/2

2. cos^-1 (1/2)

3. cos^-1(-1)

Guest Jan 4, 2015

#1**+10 **

Hints :

For question 1 and 2 use this triangle

hint for question 3.

Here is an interactive unit cirlce for trigonometry. Try and work really understand what it is telling you.

WHEN you fully understand it advanced trig will become easier.

Cos of an angle is given by the x value on the circumference of the unit circle. See if you can work out why.

http://www.mathsisfun.com/geometry/unit-circle.html

Here is a mor advanced version.

If you can work out the first one then see if you can make sense of this one.

https://www.mathsisfun.com/algebra/trig-interactive-unit-circle.html

Melody Jan 4, 2015

#1**+10 **

Best Answer

Hints :

For question 1 and 2 use this triangle

hint for question 3.

Here is an interactive unit cirlce for trigonometry. Try and work really understand what it is telling you.

WHEN you fully understand it advanced trig will become easier.

Cos of an angle is given by the x value on the circumference of the unit circle. See if you can work out why.

http://www.mathsisfun.com/geometry/unit-circle.html

Here is a mor advanced version.

If you can work out the first one then see if you can make sense of this one.

https://www.mathsisfun.com/algebra/trig-interactive-unit-circle.html

Melody Jan 4, 2015

#3**+5 **

Thanks Chris,

Those two interactive unit circles are really great. I hope people put in effort and can work out what it is that they are supposed to be learning from them.

Of course we are here to help if people want us to help them understand.

Plus I expect the mathisfun blurb that goes with them is very good.

Melody Jan 4, 2015