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Maths help: trigonometry - Printable Version

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Maths help: trigonometry by segosa on 05-06-2005 at 03:17 PM

It's probably a very simple question but I can't see how to do it. :(

quote:
Show that the equation

3tanX = 2cosX

can be expressed as

2sin²X + 3sinX - 2 = 0

X = angle
RE: Maths help: trigonometry by Mnjul on 05-06-2005 at 04:09 PM

   3tanX = 2cosX
->3(sinX/cosX) = 2cosX
->3sinX=2(cos²X)
->3sinX=2(1-sin²X)
->3sinX=2-2sin²X
->2sin²X+3sinX-2=0

(tanX=sinX/cosX and cos²X+sin²X=1)

RE: Maths help: trigonometry by RaceProUK on 05-06-2005 at 04:12 PM

[Image: attachment.php?pid=456244]
;)

Edit: :P to Mnjul - mine's formatted

And if two people do the same thing, it must be good :)

RE: Maths help: trigonometry by segosa on 05-06-2005 at 04:45 PM

Thanks, someone PMed me it after I posted it too, it was identical to Mnjul's, he should have just posted in here :p

It makes sense now, god knows why I didn't think of moving over the cosX on the bottom :(

RE: Maths help: trigonometry by spokes on 05-06-2005 at 05:12 PM

quote:
Originally posted by raceprouk
[Image: attachment.php?pid=456244]
;)

Edit: :P to Mnjul - mine's formatted

And if two people do the same thing, it must be good :)
what program creates those pictures?
RE: Maths help: trigonometry by emit on 05-06-2005 at 06:17 PM

the key to trig questions like that is memorising the list of trigonometric identities, seg.

RE: Maths help: trigonometry by segosa on 05-06-2005 at 07:59 PM

quote:
Originally posted by Time
the key to trig questions like that is memorising the list of trigonometric identities, seg.

I knew them, but I have something wrong with me whereby I miss the simplest things. :P
RE: Maths help: trigonometry by RaceProUK on 05-06-2005 at 08:34 PM

quote:
Originally posted by spokes
quote:
Originally posted by raceprouk
[Image: attachment.php?pid=456244]
;)

Edit: :P to Mnjul - mine's formatted

And if two people do the same thing, it must be good :)
what program creates those pictures?
I use Equation Editor in Word, and take a screenshot :P