Trouble Simplifying Homework Equations

  • Thread starter Thread starter ACLerok
  • Start date Start date
  • Tags Tags
    Simplifying
Click For Summary
SUMMARY

The discussion focuses on simplifying trigonometric equations, specifically transitioning from one equation to another using the identity for cosine of a sum. The relevant identity discussed is cos(θ + φ) = cos(θ)cos(φ) - sin(θ)sin(φ). The user attempts to simplify the expression by expanding cos(θ + π/4) and multiplying by √2, leading to the conclusion that a division is necessary to balance the equation, as no φ exists where both sine and cosine equal 2.

PREREQUISITES
  • Understanding of trigonometric identities, specifically cosine and sine functions.
  • Familiarity with the concept of angle addition in trigonometry.
  • Basic algebraic manipulation skills.
  • Knowledge of the unit circle and properties of sine and cosine functions.
NEXT STEPS
  • Study the derivation and applications of the cosine addition formula.
  • Explore the unit circle to understand the values of sine and cosine at various angles.
  • Practice simplifying trigonometric expressions using various identities.
  • Learn about the implications of dividing trigonometric functions and how it affects the equation.
USEFUL FOR

Students studying trigonometry, educators teaching trigonometric identities, and anyone looking to improve their skills in simplifying mathematical equations.

ACLerok
Messages
194
Reaction score
0

Homework Statement


I am reviewing some old exam solutions and came across something I cannot figure out. I'm don't understand how they simplify from the first equation to the second. I looked up a table of trig identies but could not find anything that would help.


Homework Equations


http://img296.imageshack.us/img296/864/untitledimageda3.th.jpg


The Attempt at a Solution

 
Last edited by a moderator:
Physics news on Phys.org
Expand cos ( theta + pi/4), and times it by root 2.
 
The relevant trig identity is [itex]cos(\theta+ \phi)= cos(\theta)cos(\phi)- sin(\theta)sin(\phi)[/itex]

Ignoring the 'm(t)' which just "goes along for the ride", you have [itex]2cos(\theta)- 2 sin(\theta)[/itex]. Obviously, since 2> 1, there is no [itex]\phi[/itex] that has both sine and cosine equal to 2- you will need divide by something. But you would still have [itex]cos(\phi)= sin(\phi)[/itex]. What value of [itex]\phi[/itex] has that property? And what do you then need to divide by?
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
2
Views
3K
  • · Replies 10 ·
Replies
10
Views
4K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K