Pendulum AltitudeDate: 09/26/2002 at 06:43:45 From: Relle Subject: Trigonometry This question is related to Trigonometry. A pendulum 45cm long swings through a vertical angle of 30 degrees. Find the distance of the altitude through which the pendulum bob rises. (Answer: 1.533cm) I have problems drawing (visualising) this picture, and am thus unable to solve this problem. Maybe if you could try to include a picture I'll be able to understand the answer better. Thanks. Date: 09/26/2002 at 09:17:52 From: Doctor Ian Subject: Re: Trigonometry Hi Relle, Here is a diagram of the situation: A /|\ / | \ AP = AP' = AP" / | \ / | \ P' | P" P It's not clear which of the following is the case: 1) angle P'AP" = 30 degrees 2) angle PAP" = 30 degrees I'll leave that for you to work out with your teacher. In either case, it's angle PAP" that you're interested in. Let's look more closely at that: A |\ | \ | \ | \ | \ AC is vertical | \ CP" is horizontal | \ therefore angle ACP" = 90 degrees C.......P" | P Now, note that length of AC cos(PAP") = ------------ length of AP" Can you take it from here? If you're having trouble following what I did, you might want to take a look at Trigonometry in a Nutshell http://mathforum.org/library/drmath/view/53942.html Does this help? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
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