# quadrants is it really important to say in what quadrant the angle is? Yest it is important. When we know that location of the angle, we can determine the values of the trigonometric identities.

For example:

We will compare the angle pi/3 into the first, second, third, and 4th quadrants.

If pi/3 is in the 1st quadrant:

==> cos(pi/3) = 0.5

If pi/3...

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Yest it is important. When we know that location of the angle, we can determine the values of the trigonometric identities.

For example:

We will compare the angle pi/3 into the first, second, third, and 4th quadrants.

If pi/3 is in the 1st quadrant:

==> cos(pi/3) = 0.5

If pi/3 is in the 2nd quadrant:

==> pi/3 = pi - pi/3 = 2pi/3

==> cos (2pi/3) = - 0.5

If pi/3 is in the 3rd quadrant.

==> pi/3 = pi + pi/3 = 4pi/3

==> cos(4pi/3) = - 0.5

If pi/3 is in the 4th quadrant:

==> pi/3 = 2pi - pi/3 = 5pi/3

==> cos( 5pi/3) = 0.5

Then, we notice that the sign changes as the angle changes the location.

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