Quadrantal Angles

Quadrantal Angles are angles in which the terminal side is on the x- or y-axis.  We will consider the consequence of our new definitions for such angles first.

Example 2: 

Find the trig functions of 90^o.

Solution: 

We can choose any value of r, so to make it easy, we choose r = 1.  Then the coordinates of the point on the terminal side that intersects our circle will be (0, 1):

Now we use the definitions to find the values of the trig functions.  Notice that some are "undefined" because you cannot divide by 0:

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