Exploring the Difference Quotient for f(x) = sinx

In summary, the problem involves proving that (f(x+h)-f(x))/h=((sin(h/2))/(h/2))(cos(x+h/2)) by using trigonometric identities, specifically the sum-to-product identity. The student was initially stuck but was able to figure it out with the help of the identity.
  • #1
EL ALEM
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Homework Statement


Show that if f(x)=sinx then (f(x+h)-f(x))/h=((sin(h/2))/(h/2))(cos(x+h/2)


Homework Equations


Trig identities, possibly the half angle formulas?


The Attempt at a Solution


(f(x+h)-f(x))/h
= (f(x+ h/2 + h/2)-f(x))/(h/2 + h/2)
= (sin(x+ h/2 + h/2)-sin(x))/(h/2 + h/2)
im stuck after this, don't know what to do..
 
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  • #2
Hope this isn't too much of a hint, but instead of doing what you have above, I would try to use the sum-to-product identity.
 
  • #3
Sum to product identity? Thats the first time I've heard of that one, I looked it up on wikipedia and I don't recognize at all, let alone apply it to this problem. Can you help me get started w/ it?
 
  • #4
Nevermind i got thanks a bunch for showing me that identity!
 
Last edited:

What is a difference quotient?

A difference quotient is a mathematical concept used to find the slope of a curve at a specific point. It measures the average rate of change of a function over a small interval.

Why is the difference quotient important?

The difference quotient is important because it allows us to find the slope of a curve at any point, which is necessary for understanding how a function is changing. It is also a key component in the process of finding the derivative of a function.

How is the difference quotient calculated?

The difference quotient is calculated by taking the limit as h approaches 0 of (f(x+h) - f(x))/h, where f(x) is the given function and h is a small interval around the point at which we want to find the slope.

What are some real-life applications of the difference quotient?

The difference quotient is used in various fields such as physics, economics, and engineering to analyze and model real-world phenomena. It can be used to calculate rates of change, acceleration, and other important quantities.

What are some common mistakes made when working with the difference quotient?

Some common mistakes when working with the difference quotient include forgetting to take the limit as h approaches 0, using the wrong formula, and miscalculating the value of h. It is important to carefully follow the steps and double-check calculations to avoid errors.

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