Test
Unit circle and obtuse angles
This test uses the unit circle to determine trigonometric values. Tasks cover quadrants, signs of sine and cosine, obtuse and supplementary angles and checking whether a resulting value is reasonable.
Time left: 00:00:00
Sample questions
- Give the unit-circle point coordinates for angle ___°.
- Simplify sin(180° − ___°).
- Simplify cos(180° − ___°).
- Simplify tan(180° − ___°).
- An acute angle α has sine ___. What is sin(180° − α)?
Unit circle and obtuse angles
On the unit circle, the point corresponding to angle α has coordinates (cos α, sin α). Thus sine is the y-coordinate, cosine the x-coordinate, and tan α = sin α / cos α whenever cos α ≠ 0.
Signs and reference angles
In quadrant II, sine is positive while cosine and tangent are negative. Reference angles give values such as sin(180° − α) = sin α and cos(180° − α) = −cos α. Determine the quadrant before choosing a sign.
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