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#1 2006-11-01 10:16:30

unique
Member
Registered: 2006-10-04
Posts: 419

sin cos

Evaluate:
         7pi                11pi
sin^2  ----  + cos^2 -----
            6                  6


7pi = 21.99114858 divided by 6 > 3.665191429
11pi = 34.55751919 divided by 6 > 5.759586532

sin^2 3.665191429 > isssssssss
cos^2 5.759586532 > isssssssss

HELP
do u have to do
sin 3.665191429 ^ 2 like this?

Last edited by unique (2006-11-01 10:17:05)


Desi
Raat Key Rani !

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#2 2006-11-01 10:45:42

polylog
Member
Registered: 2006-09-28
Posts: 162

Re: sin cos

means

So, you first take the sin, and then square the result:

But are you supposed to get an exact value for this ? Or is a decimal ok?

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#3 2006-11-01 10:51:21

unique
Member
Registered: 2006-10-04
Posts: 419

Re: sin cos

if i do that
than my answer comes out to
4.086538401 x10 -03
on the calculator


Desi
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#4 2006-11-01 10:56:59

polylog
Member
Registered: 2006-09-28
Posts: 162

Re: sin cos

That happens because your calculator is in Degree Mode. You need it in Radian mode, because angles like 7pi/6 are in Radians.

Last edited by polylog (2006-11-01 10:57:16)

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#5 2006-11-01 11:08:16

unique
Member
Registered: 2006-10-04
Posts: 419

Re: sin cos

oh yeah thanks
i had my calculaor on complx instead of comp


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#6 2006-11-01 11:17:16

unique
Member
Registered: 2006-10-04
Posts: 419

Re: sin cos

so answer is the total is
1.068934976

so final answer is 1.07


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#7 2006-11-01 13:01:35

polylog
Member
Registered: 2006-09-28
Posts: 162

Re: sin cos

Did you round off a lot of the numbers in between steps? I get the answer as 1 exactly...

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#8 2006-11-01 15:36:13

mathsyperson
Moderator
Registered: 2005-06-22
Posts: 4,900

Re: sin cos

Oh, of course! cos(11π/6) = cos(7π/6).

Substituting that in gets you sin²(7π/6) + cos²(7π/6), which is 1 because sin² + cos² always is.

It's so simple to work out now we know the answer. roll


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It wanted to be normal.

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