Law of Sines

1. Demonstration Teaching
In
Trigonometry

2. Right Triangle
Acute Triangle
Obtuse Triangle

3. TriangleSolved
 three sides
 three angles

4. Right Triangle

5. B
B
B
B
a
Acute TriangleObtuse Triangle
Oblique Triangles

6. Oblique Triangle

7. How then do we
solve oblique
triangles?

9. Case II: Given two
angles and the
included side between
them (ASA)
Case I: Given two
angles and a side
opposite one of them
(AAS)
Case III: Given two
sides and an angle
opposite one of them
Case IV: Given two
sides and the included
angle between them
Case v: Given three sides

10. Case I. Given two angles and a side opposite to one of them. (AAS)
Given: A = 48°
C = 102°
c = 25cm
Unknown : B , a, c
A
C
B
a=?b =?
c= 25 cm
48°
102°
?

11. Case I. Given two angles and a side opposite to one of them. (AAS)
Given: A = 63°
C = 79°
a= 12 in
Unknown : B , b, c
In ▲ABC, A = 63°, B = 79°, and a = 12 in. Find
the length s of the other two sides and the
measure of the third angle, C.
BA
C
a =12 inb =?
c= ?
63°
79°
?

12. Given: A = 75°
C = 85°
b = 10 cm
Unknown : B , a, c
Case II. Given two angles and the included side between
them. (ASA)
A B
c = ?
b=10 cm a =?
C
85°
75° ?

13. Given: A = 59°
C = 49°
b = 13 cm
Unknown : B , a, c
Case II. Given two angles and the included side between
them. (ASA)
A B
c = ?
b=13 cm a =?
C
59°
49°
?

14. is a triangle which does not
contain a right angle.
Oblique Triangle

16. Case I: Given two angles and a side opposite
one of them (AAS)

17. Case II: Given two angles and
the included side between them
(ASA)

18. Case III: Given two sides and
an angle opposite one of
them

19. Assignment:
Answer Exercises
6.2 p. 167.