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Secx-tanxsinx=1/secx

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Brad M. | Professional Tutor: Ultra Streamlined Math - Physics - AccountingProfessional Tutor: Ultra Streamlined M...
4.9 4.9 (217 lesson ratings) (217)
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Hi Tracy -- I attended Horseheads High school and will be visiting the area in coming weeks.

Sometimes it's helpful simply to plug in directly the triangle sides in each of these ratios:

secx=hyp/adj, tanx=opp/a, sinx=opp/h

h/a - opp/a(opp/h)= a/h ==> a*a/h= h*h/h - opp*opp/h :

factor out 1/h ==> a*a= h*h - opp*opp which is the <a^2 + b^2 = c^2> identity.

Any trig identity with the sides actually plugged in should land here ...   Regards & send me an Email :)

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Robert J. | Certified High School AP Calculus and Physics TeacherCertified High School AP Calculus and Ph...
4.6 4.6 (13 lesson ratings) (13)
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secx-tanxsinx

= cosx(sec^2 x - tan^2 x), factor out cosx

= cosx, since sec^2 x - tan^2 x = 1

= 1/secx