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Chapter 4

Chapter 4. Trigonometry Day 3 (Covers Topics in 4.2-4.4) Trig Angles on Unit Circle in Degrees 1 Notecard. Sketch the angle. Find the Quadrant and + or - from ASTC. Find the Reference Angle (distance to x-axis) Use the Memorized Table to get your value. Don’t forget + or -.

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Chapter 4

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  1. Chapter 4 Trigonometry Day 3 (Covers Topics in 4.2-4.4) Trig Angles on Unit Circle in Degrees 1 Notecard

  2. Sketch the angle. • Find the Quadrant and + or - from ASTC. • Find the Reference Angle (distance to x-axis) • Use the Memorized Table to get your value. Don’t forget + or -. Steps to Evaluate Trig Functions

  3. IV, sine is negative sin 330° • Sketch • Quadrant: • Ref. angle: • Answer = 360˚ - 330˚ = 30˚ - ½

  4. Cos 150˚ • Sketch • Quadrant: • Ref. angle: • Answer = II, - 180˚-150˚=30˚

  5. none, quadrantal Tan 90˚ • Sketch • Quad: • Ref. angle: none, must use coordinates from unit circle (0, 1) Tan θ = y/x =1/0 = undefined

  6. Sec -60° Sketch Quad.: Ref. angle: IV, + 60˚ Cos 60˚ = ½, so sec -60˚ = 2

  7. III, - Csc-120° • Sketch • Quad: • Ref. angle: • Sin 60˚ = so csc -120˚ = 60˚

  8. Find the quadrant for θ. • cos θ >0 and tan θ < 0. cosine is + in I, IV; tangent is – in II, IV So, they both occur in IV. • sin θ <0 and tan θ>0. sine is – in III, IV; tangent is + in I, III So, they both occur in III.

  9. Cos θ= and sinθ>0. Find the other 5 trig. values. Answer: Cosine is – in II, III. Sine is + in I, II. So, they both occur in II. Draw triangle in Quad. II. Label adjacent -24 and Hypotenuse 25. Use Pyth. Thm. To find other side. Sinθ= 7/25 cscθ=25/7 cosθ = -24/25 secθ = -25/24 tanθ = -7/24 cotθ = -24/7 25 7 θ -24

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