SOLUTION: Can somebody help me by writing 4 cos 2θ sin 4θ as a sum or difference? Ty.

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Question 1067701: Can somebody help me by writing 4 cos 2θ sin 4θ as a sum or difference? Ty.
Found 2 solutions by stanbon, ikleyn:
Answer by stanbon(75887)   (Show Source): You can put this solution on YOUR website!
Can somebody help me by writing 4 cos 2θ sin 4θ as a sum or difference?
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a+b = 40
a-b = 20
----
2a = 60
a = 30
Then b = 10
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4[cos(20)*sin(40)] = 4[cos(20-40)+cos(20+40)]
= 4[cos(20)+cos(60)]
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Cheers,
Stan H.
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Answer by ikleyn(52788)   (Show Source): You can put this solution on YOUR website!
.
Can somebody help me by writing 4*cos(2*theta)*sin(4*theta) as a sum or difference? Ty.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 

There is a general formula of Trigonometry

.


See any serious textbook in Trigonometry or the lessons

    - FORMULAS FOR TRIGONOMETRIC FUNCTIONS

    - Product of trigonometric functions

in this site. 


This formula is FUNDAMENTAL, which means "everybody must know it".


According to this formula,

 =  = .

Answer. = .



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