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Sir, this is a broader and clearer image than the former one. Please give me the solutions.

Question image for Sir, this is a broader and clearer image than the
Profile image of Abhay
7 Years agoGrade Select Grade
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1 Answer

Profile image of Snehal Jadhav
7 Years ago
The 35th question demands for the expansion of cos 5x:
cos 5x = cos(3x + 2x)
 
We, can use the formula :
cos(a+b)=cos(a)cos(b) – sin(a)sin(b)
 
cos(3x + 2x)=cos3xcos2x – sin2xsin3x
 
For, further expansion we can use below given formulas:
  1. cos3x=4cos3x – 3cosx
  2. cos2x=2cos2x – 1
  3. sin3x=3sinx – 4sin3x
  4. sinx=2sinxcosx
  5. sin2x=1 – cos2x
Please subsitute the values using these formulas:
 
cos 5x=16cos5x – 20cos3x + 5cosx
 
By, comparing the main equation to derived equation we get :
 
a = 16, b= – 20, c=5
 
So, a+b+c=16 – 20 +5
     =1
 

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