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# What are the steps and the answers to this problem?

4-4cos(π/5)

### 2 Answers by Expert Tutors

Philip P. | Effective and Affordable Math TutorEffective and Affordable Math Tutor
5.0 5.0 (428 lesson ratings) (428)
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Assuming that the argument of the cosine is pi/5 rather than n/5 (the pi character (π) from the special characters set above (Ω) comes out looking like an n).  I'll use the word pi rather than the symbol:
1. First compute the cos(pi/5) = cos(0.628 radians) = 0.809
2. Next multiply cos(pi/5) by 4 = 4*(.809) = 3.236
3. Now subtract 3.236 from 4: 4-3.236 = 0.764

The priorities of the operations are:
1. Do the math inside the argument of the cos first, e.g. π/5
2. Then take the cosine of the argument
3. Then multiply the value of the cosine by the constant 4
4. Then subtract all that from 4
5.0 5.0 (54 lesson ratings) (54)
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4 - 4cos(n/5) = 0

I assume you are trying to find the value for n

subtract 4 from each side

-4cos(n/5) = -4

divide by 4

cos(n/5) = 1

in the interval 0, 2PI

cos (n/5) = 1 when (n/5) = 0   or n = 0

and cos(n/5) = 1 when n/5=2PI  or n = 2pi/5

if there is no restriction on the interval

Then cos(n/5) =1 when n/5= 2*x*PI and      n = 2/5*x*PI   where x are all the interger values