# Thread: Calculate the principle angle?

1. ## Calculate the principle angle?

I am having some trouble with this question.

It says here:

A point is given on the terminal arm of each angle. Calculate the measure of the principal angle in radians to 1 decimal place.

a) (2, 3)
b) (-3, 1)

How do you figure this out? Thanks!

2. Originally Posted by finalfantasy
I am having some trouble with this question.

It says here:

A point is given on the terminal arm of each angle. Calculate the measure of the principal angle in radians to 1 decimal place.

a) (2, 3)
b) (-3, 1)

How do you figure this out? Thanks!
In a) we are talking about a quadrant I angle, so you solve
$\displaystyle tan ( \theta ) = \frac{3}{2}$

So put your calculator in "radian" mode, and figure out what the angle is.

-Dan

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# how do i find the principal angle

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