Proving Trig Identities: Is this Question Referring to the Pythagorean Identity?

Click For Summary
SUMMARY

The discussion centers on proving the trigonometric identity sec θ (sec θ - cos θ) = tan² θ. Participants clarify that sec θ is defined as 1/cos θ, and they explore the relationship between sec θ and the Pythagorean identity 1 + tan² θ = sec² θ. The solution involves manipulating the expression by substituting sec θ and simplifying the equation to demonstrate the identity. The conclusion confirms that the problem indeed relates to the Pythagorean identity.

PREREQUISITES
  • Understanding of trigonometric functions: secant, tangent, and cosine
  • Familiarity with the Pythagorean identity in trigonometry
  • Basic algebraic manipulation skills
  • Knowledge of trigonometric identities and their proofs
NEXT STEPS
  • Study the derivation of the Pythagorean identity 1 + tan² θ = sec² θ
  • Practice proving various trigonometric identities using algebraic techniques
  • Explore the relationship between secant and cosine functions in depth
  • Learn about other trigonometric identities such as co-function identities and reciprocal identities
USEFUL FOR

Students studying trigonometry, educators teaching trigonometric identities, and anyone looking to strengthen their understanding of trigonometric proofs and relationships.

priscilla98
Messages
93
Reaction score
0

Homework Statement


Prove Trig. Identities

1. sec θ (sec θ - cos θ)= tan^2 θ

Homework Equations



sec θ = 1/cos θ
tan θ = sin θ/ cos θ
cot θ = cos θ / sin θ

The Attempt at a Solution



1. sec θ * sec θ - sec θ * cos θ

1/ cos θ * 1/ cos θ - 1/ cos θ * cos θ

----> cos θ is crosses out by the right but I am confused on 1/cos θ. I know 1/cos θ = sec θ. Wait does this problem refer to the pythagorean identity which is 1 + tan^2 θ = sec^2 θ
 
Physics news on Phys.org
priscilla98 said:

Homework Statement


Prove Trig. Identities

1. sec θ (sec θ - cos θ)= tan^2 θ

Homework Equations



sec θ = 1/cos θ
tan θ = sin θ/ cos θ
cot θ = cos θ / sin θ

The Attempt at a Solution



1. sec θ * sec θ - sec θ * cos θ

1/ cos θ * 1/ cos θ - 1/ cos θ * cos θ

----> cos θ is crosses out by the right but I am confused on 1/cos θ. I know 1/cos θ = sec θ. Wait does this problem refer to the pythagorean identity which is 1 + tan^2 θ = sec^2 θ

Use = !
Generally you want to start on one side and end up with the expression on the other side.

sec θ * sec θ - sec θ * cos θ = sec2θ - 1 = ?

In answer to your question, yes.
 
Thanks a lot :)
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
Replies
5
Views
3K
Replies
17
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
Replies
5
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 10 ·
Replies
10
Views
3K