Example: Express sin 120⁰ as a function of an acute angle (an angle between 0⁰ and 90⁰).
Solution:
Each angle θ whose terminal side lies in quadrant II, III, or IV has associated with it an angle called the reference angle, alpha (alpha is formed by the x-axis and the terminal side).
Since 120⁰ lies on the second quadrant, then alpha = 180⁰ - 120⁰ = 60⁰.
Since sine is positive in the second quadrant, sin 120⁰ = sin 60⁰.
Example: Express tan 320⁰ as a function of an acute angle.
Solution:
Since 320⁰ lies on the fourth quadrant, then alpha = 360⁰ - 320⁰ = 40⁰.
Since tangent is negative in the fourth quadrant, tan 320⁰ = -tan 40⁰.
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It's called an acute angle.An Acute angle.
That would be an acute angle.
No because it's a right angle
An acute angle
It is an acute angle.