1. Math 20-1 Chapter 2 Trigonometry
Teacher Notes
Math Chapter 2 Trigonometry
2.3 The Sine Law

2. 2.3 The Sine Law 30° Angle or ratio? 0.174 Angle or ratio?
Math Chapter 1 Sequences and Series
2.3 The Sine Law
Trig Equations
30°
Angle or ratio?
0.174
Angle or ratio?
Angle or ratio?
2.3.1

3. ? Solving Non-Right Triangles with Primary Trig Ratios
Stan observes that the angle of elevation of a plane to be 510.
At the same time, Paul observes it to be The pilot used a range finder to determine that Stan is m from the plane and Paul is m from the plane. How far apart are Stan and Paul?
(nearest m) m m
Paul
Stan
510
340 ?
2.3.2

4. ? Solving with Primary Trig Ratios Alternate method:
510
340 A B C
Stan
Paul m ? m D
Alternate method:
Solve non-Right Triangle
Total Distance = BD + CD
Stan and Paul are 340 m apart
2.3.3

5. An oblique triangle is a triangle that does not contain a right angle.
Using the definition of sine ratio: A B C b c a
Isolate the variable h: h D
Using the Transitive Property:
Divide by bc
Divide by sinBsinC
2.3.4

6. The Law of Sines
For an oblique triangles or right triangles, when you are given SSA or ASA: a b c B C A
2.3.5

7. Proving Equivalence 30° 2 What do you notice about each ratio? 3 60°1
60°
30° 2
What do you notice about each ratio?
Would equivalence change if the reciprocals were written?

8. A S S ? or Solving with Primary Trig Ratios
Alternate method: Solve non-Right Triangle
510
340 A B C
Stan
Paul m ? m
Given: two angles and one side or
two sides and an angle opposite one of the given sides S S
950
How would the solution be affected if you would have chosen
Stan and Paul are 340 m apart or
2.3.6

9. Applying the Law of Sines (nearest 100th for lengths, 10th for angles)
600 c
1800- ( ) = 600
c = 12.25
2.3.7

10. Assignment Suggested Questions Page 97: 10, 15
Page 108: 1a, 2a, 3a, 5a, 11, 13, 19
2.3.8