Trigonometry Preparing for math contest; Please help

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SUMMARY

The discussion focuses on proving the conditions for triangle ABC to be acute, right, or obtuse based on the relationship between the angles alpha and beta. It establishes that the triangle is acute if and only if tan(alpha) * tan(beta) > 1, right if tan(alpha) * tan(beta) = 1, and obtuse if tan(alpha) * tan(beta) < 1. The proof involves manipulating trigonometric identities and understanding the angle k, defined as k = alpha + beta, with specific ranges for acute, right, and obtuse triangles.

PREREQUISITES
  • Understanding of trigonometric functions, specifically tangent
  • Knowledge of triangle properties and classifications (acute, right, obtuse)
  • Familiarity with trigonometric identities and equations
  • Basic algebraic manipulation skills
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  • Study the properties of tangent functions in trigonometry
  • Explore proofs involving triangle inequalities and angle sums
  • Learn about trigonometric identities and their applications
  • Investigate the implications of angle classifications on triangle geometry
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Students preparing for math contests, educators teaching trigonometry, and anyone interested in advanced geometric proofs and properties of triangles.

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Prove that the triangle ABC is:

a) acute, if and only if tan(alfa)*tan(beta)>1
b) right, if and only if tan(alfa)*tan(beta)=1
c) obtuse, if and only if tan(alfa)*tan(beta)<1
 
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start with the following...
k=alpha+beta
90<k<180 in an acute triangle
k=90 in a right triangle
k<90 in an obtuse triangle

(sinx/cosx)(sin(k-x)/cos(k-x))
=(sinxsinkcosx-cosksin^2x)/(cos^2xcosk+sinksinxcosx)
sinxsinkcosx=A and cosk=B
(A-Bsin^2x)/(A+Bcos^2x)= (A-Bsin^2x)/(A+B-Bsin^2x)
we then want B equal to zero. cosk=0 when k=90. when k is greater B becomes negative.
 
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