Contents

Sine Rule

Solution of Triangle (Sine)

Cosine Rule

Solution of Triangle (Cosine)

Quiz 

Trigonometry Main Page

Solution of Triangle (Sine)

The Sine Rule is used to solve any problems involving triangles when at least either of the following is known:

Example 1 (Given two angles and a side)

In triangle ABC, ÐA = 59°, ÐB = 39° and a = 6.73cm. Solve the triangle. 

  ÐC = 180° - (39° + 59°)

 

Example 2 (Given two sides and an acute angle)

Solve triangle ABC in which ÐA = 55°, b = 16.3cm and and a = 14.3cm

  

 

  ÐC = 56°, ÐB = 59° and c = 14.47cm

 

Example 3 (Given two sides and an obtuse angle)

 

Solve triangle ABC in which ÐA =100°, b = 5cm and a = 7.7cm

 

   

 

ÐB = 39.8°, ÐC = 40.2° & c = 5.05cm