Anti-Differentiation involving sin and cos?

2009-08-20 8:29 am
I am anti-differentiating the following:
f(x)=4sin2x

therefore the answer is (correct me if im wrong): -2cos2x
If i anti-dif that again it will be: sin2x

This is supposed to be repeated for numerous times, enough to allow me to see a pattern and produce an equation that will enable me to solve the 127th integration.

therefore:
f(x)=4sin2x
1) -cos2x
2) sin2x
3) -0.5cos2x
4) 0.25sin2x
5) -0.125cos2x


My question is, is it true to say that
COS will always be NEGATIVE
and SIN will always be POSITIVE?

You can also help with the part that involves producing an equation if you like

Note: the constant of integration (c) is are zero which is why they are not shown in the above list.

回答 (3)

2009-08-20 10:49 am
✔ 最佳答案
You are correct:

COS will always be NEGATIVE
and SIN will always be POSITIVE

This is what you got and you are correct. I think it will be easier to come up with 127th if we look at the fraction

Let N = nth derivative

notice if N = even, we have positive sin 2x and if N = odd, we have negative cos 2x

We have this pattern:

if N = even: (1/2)^(N-2)*sin (2x)
if N = odd: - (1/2)^(N - 2)*cos (2x)

N = 127: - (1/2)^(127-2)*cos (2x)

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Lets see your anti-derivative

N = 2, even: sin2x = (1/2)^(2-2)sin 2x

N = 3, odd : -0.5cos2x = - (1/2) ^(3 - 2)cos 2x

4) 0.25sin2x = (1/2)^(4 - 2)sin 2x = (1/2)*(1/2) sin2x

5) -0.125cos2x = - (1/2)^(5 - 2) cos 2x

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I forgot to say that N starts at 2 for this pattern
2016-12-16 11:36 pm
1a. v = 10 = 6+ 8sin ½t 4 = 8sin ½t ½ = sin ½t arcsin ½ = ½t t = 2arcsin ½ t = 2(?/6) = ?/3 b. a = dv/dt = 4 cos(½t) a(0) = 4 cos 0 = 4(a million) = 4 2. you have to be greater sparkling with your fact of the challenge via using parentheses. There are 3 obtainable approaches to interpret what you have written above.
2009-08-20 10:17 am
You are incorrect, cos will not always be negative and sin will not always be positive.

You should get something that follows this cycle:

sin antidifferentiates to -cos
-cos antidifferentiates to -sin
-sin antidifferentiates to cos
cos antidifferentiates to sin
sin antidifferentiates to -cos

and so on.

f(x) = 4sin2x
1).-2cos2x
2) -sin2x
3). 0.5cos2x
4) 0.25sin2x
5) -0.125cos2x


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