Find the locations where the slope = 0

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In summary, the conversation discusses a test question involving differentiation. The result of y' is given as 2sinxcosx - sinx, and the individual is trying to find where the slope is 0. They mention two possible approaches - rewriting the equation as sin2x - sinx or factoring out a sine. The first approach gives solutions of x = pi/3 + 2pi*k and x = 5pi/3 + 2pi*k, while the second approach gives the solution of cosx = 1/2 and x = pi/3 + 2pi*k. The individual is questioning their logic and asks for clarification. The expert summary clarifies that x = pi*k are not the only
  • #1
Feodalherren
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Homework Statement


I just had a test I can't remember exactly how the question went but it was a relatively easy differentiation problem. I can only remember my result, which was

y' = 2sinxcosx - sinx


Homework Equations





The Attempt at a Solution



I noticed that 2sinxcosx is also sin2x so you could rewrite it as Sin2x - Sinx

Now, to find the places where the slope is 0 i obviously just set it to 0 and solve. My problem was that I didn't know if I should go the Sin2x - Sinx route or Factor out a sine and do it like thisL

sinx(2cosx -1) = 0

cosx = 1/2

x = ∏/3 +2∏k

x = 5∏/3 + 2∏k

where k is any integer


The above one is the route I chose to take at the end. However, if I solve for sin2x - sin x = 0

I can just say, ∏k, where k is any integer? Where is my logic flawed?
 
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  • #2
Feodalherren said:

Homework Statement


I just had a test I can't remember exactly how the question went but it was a relatively easy differentiation problem. I can only remember my result, which was

y' = 2sinxcosx - sinx


Homework Equations





The Attempt at a Solution



I noticed that 2sinxcosx is also sin2x so you could rewrite it as Sin2x - Sinx

Now, to find the places where the slope is 0 i obviously just set it to 0 and solve. My problem was that I didn't know if I should go the Sin2x - Sinx route or Factor out a sine and do it like thisL

sinx(2cosx -1) = 0

cosx = 1/2

x = ∏/3 +2∏k

x = 5∏/3 + 2∏k

where k is any integer


The above one is the route I chose to take at the end. However, if I solve for sin2x - sin x = 0

I can just say, ∏k, where k is any integer? Where is my logic flawed?

x=pi*k aren't the only solutions to sin(2x)-sin(x)=0. They are just some of them. You've found the others in your first analysis. If sin(x)*(2*cos(x)-1)=0 then either sin(x)=0 or 2*cos(x)-1=0.
 
  • #3
Thanks for the answer though.
 
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FAQ: Find the locations where the slope = 0

What does it mean when the slope = 0?

When the slope of a line is equal to 0, it means that the line is horizontal and has no steepness or inclination. This indicates that the line is neither increasing nor decreasing and is considered a constant.

Why is it important to find locations where the slope = 0?

Finding locations where the slope = 0 is important because it helps us identify critical points on a graph, such as local maximums or minimums. These points can provide valuable information about the behavior of a function or relationship between variables.

How do you determine the slope = 0 of a line?

To determine where the slope of a line is equal to 0, you can either graph the line and visually identify the points where it is horizontal, or you can use the equation y = mx + b and set the value of m (slope) to 0, then solve for x.

Can the slope = 0 at more than one point?

Yes, the slope of a line can be equal to 0 at more than one point. This can happen when the line is completely horizontal, meaning it has no steepness or inclination. In this case, every point on the line would have a slope of 0.

What does it mean when the slope = 0 at a specific point on a graph?

If the slope of a line is equal to 0 at a specific point on a graph, it means that the line is not changing at that point. This could indicate a local maximum or minimum, or a point of inflection. It is important to analyze the behavior of the line on either side of this point to understand its significance.

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