Creating Unit Circle

Which is the length of the radius of a unit circle?

What is the x-value on the unit circle at an angle of 90°?

What is the x-value on the unit circle at an angle of -30°?

What is the y-value on the unit circle at an angle of -120°?

What is the exact coordinates of  3π/4 on the unit circle?

• (−√2∕2, √2∕2)

• (−√2∕2, −√2∕2)

• (−√3∕2, −√2∕2)

• (√2∕2, −√2∕2)

What is the radius of a unit circle?

Mathematical Equivalence

ON

What is the length of the radius of a unit circle?

• one unit

• pi units

• radians

• diameter

Unlike right triangle trigonometry, sine and cosine may be negative. Thinking about how sine, cosine, and tangent relate to (x,y) coordinate pairs on the unit circle, find the quadrants where: cosine is positive: ​ (a)   ​& (b)   cosine is negative: ​ ​ (c)   &​ (d)  

• I

• IV

• II

• III