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Problem

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Textbook Expert
Textbook ExpertVerified Tutor
24 Nov 2021

Given information

The subtraction formula for cosine is:  

The given figure is:

Step-by-step explanation

Step 1.
  • The law of cosines states that where , and   are the lengths of sides of triangle and   is the angle between the sides with lengths and  
  • From the figure, in the triangle ,  it can be noticed that:

 

 

 

 

  • Substitute the values of , , and   in the law of cosines.

 

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