2. Standard Position
An angle with its vertex at the origin.
The initial side lies along the positive
x-axis.
3. Quadrantal Angle
When the terminal side coincides with
one of the axes.
900
00 or
1800
3600
2700
4. Acute Angle
If the terminal side falls in the first
quadrant it is said to be an acute angle.
Generally talking about an angle formed
in the normal way (standard position),
positive or counter clock wise.
5. Obtuse Angle
If the terminal side falls in the second
quadrant it is said to be an obtuse angle.
Generally talking about an angle formed
in the normal way (standard position),
positive or counter clock wise.
6. Coterminal Angles
Two angles in standard position that
share the same terminal side.
Angles that differ by multiples of 3600.
Every angle has infinitely many
coterminal angles. (α + 360ko)
α – angle
k - integer
7. Reference Angle
For any angle α , 0o < α < 360o
The reference angle is the acute angle
formed by the terminal side and the
closest x-axis.
8. The Unit Circle
A circle with a radius of 1
It’s center is at the origin
Symmetric to the x-axis, the y-axis, and the
origin
9. Sine and Cosine
Ifthe terminal side of an angle θ
in standard position intersects
the unit circle at P(x, y), then
cos θ = x and sin θ = y.
Sine and cosine always range
between -1 and 1.