Help with Proving Trigonometric Identities

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SUMMARY

The forum discussion focuses on proving two trigonometric identities: (sec²x - 1) / sec²x = sin²x and cos²x / (1 + tan²x) = cot²x. The first identity can be simplified using the relationship tan²x = sin²x / cos²x, leading to the conclusion that the left-hand side equals sin²x. The second identity requires recognizing that cotx = 1/tanx, and further simplification reveals the correct form. Participants emphasize the importance of understanding fundamental trigonometric relationships for solving these proofs.

PREREQUISITES
  • Understanding of basic trigonometric identities (e.g., secant, tangent, cotangent)
  • Familiarity with algebraic manipulation of trigonometric functions
  • Knowledge of the Pythagorean identity: sin²x + cos²x = 1
  • Ability to simplify fractions involving trigonometric functions
NEXT STEPS
  • Study the derivation of the Pythagorean identities in trigonometry
  • Learn how to manipulate and simplify trigonometric expressions
  • Explore the relationships between different trigonometric functions, such as cotangent and tangent
  • Practice solving various trigonometric identities to enhance problem-solving skills
USEFUL FOR

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

chase222
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I need help solving these 2 proofs:

(sec^2x-1)/(sec^2x) = sin^2x
I am not sure what direction to go in. I know the top of the left side could be changed into:
tan^2x/sec^2x, but I don't know what to do after that.

The second one I need help with is:

cos^2x/(1+tan^2x) = cot^2x
I simplified it into:
cos^2x/sec^2x = cos^2x/sin^2x, but I don't know what to do after that. Can you help me get the next few steps of these problems? Thanks!
 
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Actually, your already done...you just don't know it.

chase222 said:
(sec^2x-1)/(sec^2x) = sin^2x
I am not sure what direction to go in. I know the top of the left side could be changed into:
tan^2x/sec^2x, but I don't know what to do after that.

remember that tanx=sinx/cosx? try that

chase222 said:
The second one I need help with is:

cos^2x/(1+tan^2x) = cot^2x
I simplified it into:
cos^2x/sec^2x = cos^2x/sin^2x, but I don't know what to do after that. Can you help me get the next few steps of these problems? Thanks!

this one is done. again, remember that cotx=1/tanx, so what is cotx in terms of sin and cos?
 
chase...u seem to be a small boy just starting to learn math...am i right?

first problem...sec^2 x-1/sec^2 x=sin^2 x...
ie...tan^2 x/sec^2 x=RHS
ie...sin^2 x*cos^2 x/cos^2 x...that is equal to sin^2 x...isnt it?/
and the second problem u have given is wrong...there is some mistake in it...dont worry..trigonometry is easy...just try to create equations urselves...solve most of them using mind...then take ur pen...because u should be learning them like drinking water...so have them in ur fingertips...
 

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