Math

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Use Newton's method to approximate a root of the equation 5sin(x)=x as follows.
Let x1=2 be the initial approximation.
The second approximation x2 is:
and the third approximation x3 is:

• Math -

5 sin x = x
let y = x - 5 sin x, search for y = 0
dy/dx = y' = 1 - 5 cos x
Xn+1 = Xn + y(Xn)/y'at Xn
X1 = 2
y = 2 - 5 sin 2 = 2 - 4.54 = -2.54
y'=1 - 5 cos 2 = 3.08
X2 = 2 -2.54/3.08 = 1.17

y = 1.17 - 5 sin 1.17 = -3.43
y' = 1 - 5 cos 1.17 = -.951
X3 = 1.17 -3.43/-.951 = 4.77

This is unlikely to work the way you want because you are jumping from cycle to cycle of the original sine wave

• Math -

The answers are wrong for this one.

• Math - sign wrong -

sorry, sign wrong. I drew my picture wrong
5 sin x = x
let y = x - 5 sin x, search for y = 0
dy/dx = y' = 1 - 5 cos x
Xn+1 = Xn - y(Xn)/y'at Xn
X1 = 2
y = 2 - 5 sin 2 = 2 - 4.54 = -2.54
y'=1 - 5 cos 2 = 3.08
X2 = 2 + 2.54/3.08 = 2.82

y = 2.82 - 5 sin 2.82 = 1.24
y' = 1 - 5 cos 2.82 = 5.74
X3 = 2.82 -1.24/5.74 = 2.60

• Math - sign wrong -

The answer is still wrong :(

• Math -

check my arithmetic carefully

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