Help w/ the difference quotient

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SUMMARY

The discussion focuses on demonstrating the difference quotient for the function f(x) = sin(x). The key equation derived is (f(x+h)-f(x))/h = (2sin(h/2)cos((2x+h)/2))/h. The user initially struggled with simplification but successfully applied the sum-to-product identity to progress. The final expression showcases the relationship between the sine function and its derivative using trigonometric identities.

PREREQUISITES
  • Understanding of trigonometric functions, specifically sine.
  • Familiarity with the difference quotient in calculus.
  • Knowledge of trigonometric identities, particularly the sum-to-product identities.
  • Basic algebraic manipulation skills.
NEXT STEPS
  • Study the derivation of the derivative of sine using limits.
  • Learn about the application of sum-to-product identities in trigonometry.
  • Explore the concept of the difference quotient in calculus in greater depth.
  • Investigate the half-angle formulas and their applications in calculus.
USEFUL FOR

Students studying calculus, particularly those focusing on trigonometric functions and their derivatives, as well as educators seeking to clarify the difference quotient concept.

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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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Ok so I used the sum to product identity and ended up w/ this

(2sin(h/2)cos((2x+h)/2))/h

not sure how to simplify it further

NM got it.
 
Last edited:

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