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April 29, 2024, 01:44:50 pm

Author Topic: Hardly seen question (don't know if it exists)  (Read 766 times)  Share 

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NeedAspirin

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Hardly seen question (don't know if it exists)
« on: November 06, 2011, 09:13:10 pm »
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Is it possible to have a question like this or similar to this:

cos^2(x)=a (a is just some random number)

If so, how do you solve it?


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Re: Hardly seen question (don't know if it exists)
« Reply #1 on: November 06, 2011, 09:17:46 pm »
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cos^2(x) = a
Take the +or- square root of both sides.
cos(x) = +or- sqrt(a)
Now take the arccos of both sides:
x = arccos(sqrt(a)) or x = arccos(-sqrt(a))
In other words, the solutions between the interval [0, 2pi] are:
x = arccos(sqrt(a)), x = pi - arccos(sqrt(a)), x = pi + arccos(sqrt(a)) and x = 2pi - arccos(sqrt(a))
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tony3272

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Re: Hardly seen question (don't know if it exists)
« Reply #2 on: November 06, 2011, 09:26:54 pm »
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For this case though you would provide a general solution for and

For :



For :

  *Edit* forget this line since it's wrong (I forgot that it's negative) go to next

or


This is assuming a is between 0 and 1, otherwise there is no solution.
« Last Edit: November 06, 2011, 09:37:28 pm by tony3272 »
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dc302

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Re: Hardly seen question (don't know if it exists)
« Reply #3 on: November 06, 2011, 09:33:55 pm »
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For this case though you would provide a general solution for and

For :



For :




This is assuming a is between 0 and 1, otherwise there is no solution.

No real solution at least. :P
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NeedAspirin

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Re: Hardly seen question (don't know if it exists)
« Reply #4 on: November 06, 2011, 09:43:31 pm »
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Thanks, for answering!