PROVing trigonometry indenties

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SUMMARY

The discussion centers on proving the trigonometric identity (tanx - cosecx)² - (cotx - secx)² = 2(cosecx - secx). The user provided a detailed attempt at the solution, utilizing fundamental trigonometric identities such as tanx = sinx/cosx, cotx = cosx/sinx, cosecx = 1/sinx, and secx = 1/cosx. After a series of algebraic manipulations, the user encountered a mistake related to the signs in their calculations, which was pointed out by another participant, leading to the successful resolution of the problem.

PREREQUISITES
  • Understanding of basic trigonometric identities (tan, cot, sec, cosec)
  • Proficiency in algebraic manipulation of trigonometric expressions
  • Familiarity with the concept of proving mathematical identities
  • Ability to use parentheses effectively to clarify operations
NEXT STEPS
  • Study the derivation and application of trigonometric identities in proofs
  • Practice solving trigonometric equations using algebraic techniques
  • Learn about common pitfalls in trigonometric manipulations, particularly sign errors
  • Explore advanced trigonometric identities and their proofs
USEFUL FOR

Students studying trigonometry, mathematics educators, and anyone looking to strengthen their skills in proving trigonometric identities.

ytx123
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Homework Statement


(tanx - cosecx)2 - (cotx - secx)2 = 2(cosecx - secx)

Homework Equations


tanx = sinx/cosx
cotx = 1/tanx = cosx/sinx
cosecx = 1/sinx
secx = 1/cosx

The Attempt at a Solution



LHS = (tanx-cosecx)(tanx-cosecx) - (cotx-secx)(cotx-secx)
= tan2x - tanxcosecx - tanxcosecx + cosec2x - cot2x + cotxsecx + cotxsecx
= sin2x/cos2x - (sinx/cosx)(1/sinx) - (sinx/cosx)(1/sinx) + 1/sin2x - cos2x/sin2x + (cosx/sinx)(1/cosx) + (cosx/sinx)(1/cosx) - (1/cos2x)
= sin2x/cos2x - 2sinx/sinxcosx + 1/sin2x - cos2x/sin2x + 2cosx/sinxcosx - 1/cos2x
= sin2x-1 / cos2x + 1 - cos2x / sin2x - 2sinx+2cosx/sinxcosx
= -1 + 1 - 2sinx+2cosx / sinxcosx
= 2sinx + 2cosx / sinxcosx

and I'm stucked
help thanks in advance :)
ps. if i post in the wrong place I am sry cos I am new :/
 
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ytx123 said:
LHS = (tanx-cosecx)(tanx-cosecx) - (cotx-secx)(cotx-secx)
= tan2x - tanxcosecx - tanxcosecx + cosec2x - cot2x + cotxsecx + cotxsecx
= sin2x/cos2x - (sinx/cosx)(1/sinx) - (sinx/cosx)(1/sinx) + 1/sin2x - cos2x/sin2x + (cosx/sinx)(1/cosx) + (cosx/sinx)(1/cosx) - (1/cos2x)
= sin2x/cos2x - 2sinx/sinxcosx + 1/sin2x - cos2x/sin2x + 2cosx/sinxcosx - 1/cos2x
= sin2x-1 / cos2x + 1 - cos2x / sin2x - 2sinx+2cosx/sinxcosx
= -1 + 1 - 2sinx+2cosx / sinxcosx
= 2sinx + 2cosx / sinxcosx

You need to use parentheses to clarify addition vs division to avoid making trivial mistakes. You missed a minus sign that's present in the part I bolded. With the correct signs in the last line, you can divide through to obtain the desired result.
 
oh! thanks for pointing out my mistake , I've got the answer already :D thanks
 

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