How do I solve for the solutions of sin 2θ = sin θ in degrees?

  • Thread starter Thread starter patriots1049
  • Start date Start date
  • Tags Tags
    Trigonometric
Click For Summary
SUMMARY

The equation sin 2θ = sin θ can be solved using the identity sin 2θ = 2sinθcosθ. By setting 2sinθcosθ = sin θ, we can isolate sinθ and cosθ. The solutions for θ include 0 degrees and 180 degrees, as these satisfy sin(θ) = 0. However, the complete solution set must also consider values of θ where cos(θ) = 1, leading to additional solutions within the range of 0 to 360 degrees.

PREREQUISITES
  • Understanding of trigonometric identities, specifically sin 2θ = 2sinθcosθ
  • Knowledge of solving trigonometric equations
  • Familiarity with the unit circle and angle measures in degrees
  • Ability to manipulate algebraic expressions involving trigonometric functions
NEXT STEPS
  • Study the unit circle to understand the angles where sin(θ) = 0 and cos(θ) = 1
  • Learn about the general solutions for trigonometric equations
  • Explore the implications of periodicity in trigonometric functions
  • Practice solving similar trigonometric equations with different identities
USEFUL FOR

Students studying trigonometry, educators teaching trigonometric identities, and anyone preparing for mathematics exams involving trigonometric equations.

patriots1049
Messages
10
Reaction score
0

Homework Statement


sin 2θ = sin θ Find the solutions in degrees.


Homework Equations



sin 2θ = 2sinθcosθ

The Attempt at a Solution


sin 2θ = sin θ
2sinθcosθ = sin θ
sinθ *cosθ/sin θ = 1

That's as far as I can get, and I think that is wrong. How do I procede from 2sinθcosθ = sin θ?
 
Physics news on Phys.org
patriots1049 said:

Homework Statement


sin 2θ = sin θ Find the solutions in degrees.


Homework Equations



sin 2θ = 2sinθcosθ

The Attempt at a Solution


sin 2θ = sin θ
2sinθcosθ = sin θ
One obvious possibility is sin(\theta)= 0. What values of \theta give that?
IF sin(\theta)\ne 0, you can divide by it.

sinθ *cosθ/sin θ = 1
So cancel the sin(\theta)s, giving cos(\theta)= 1[/math]. What values of \theta give that?<br /> <br /> <blockquote data-attributes="" data-quote="" data-source="" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch"> <div class="bbCodeBlock-content"> <div class="bbCodeBlock-expandContent js-expandContent "> That&#039;s as far as I can get, and I think that is wrong. How do I procede from 2sinθcosθ = sin θ? </div> </div> </blockquote>
 
Therefore the answer would be 0 degrees and 180 degrees? The book states that answers must greater or equal to one and less than 360.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
13
Views
2K
Replies
5
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 16 ·
Replies
16
Views
8K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K