Download Trigonometry Lecture Notes, Section 7.1

Trigonometry Lecture Notes
Section 7.1
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Section 7.1: Oblique Triangles and the Law of Sines
Big Idea: The Law of Sines relates the angles and side lengths for any triangle. The Law of
Sines comes from subdividing a triangle into two right triangles using an altitude, and then
working out multiple equal expressions for the altitude.
Big Skill: You should be able to apply the Law of Sines to solve triangles.
The Law of Sines
a
b
c


sin A sin B sin C
OR
sin A sin B sin C


a
b
c
Proof:
Trigonometry Lecture Notes
Practice:
1. Solve:
Section 7.1
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Trigonometry Lecture Notes
2. Solve:
Section 7.1
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Trigonometry Lecture Notes
Section 7.1
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3. Suppose you measure the angle of elevation to the top of a building to be 48.2, then you
step back 52.7’, and measure the new angle of elevation to be 37.9. If your measuring
instrument is 6’ above the ground, what is the height of the building?
Trigonometry Lecture Notes
Section 7.1
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Area of a Triangle
1
A  bc sin  A 
2
OR
1
A  ab sin  C 
2
OR
1
A  ac sin  C 
2