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

2 years ago

Answers : (1)

Snehal Jadhav
54 Points
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
2 years ago
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