I would be very grateful if someone could solve this question for me???

Using the identities for sin (A+B) and cos^2(theta)+sin^2(theta)=1

Find sine 65 degrees?

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- August 8th 2010, 07:04 PMGAVREED2Trigonometric Identities problem
I would be very grateful if someone could solve this question for me???

Using the identities for sin (A__+__B) and cos^2(theta)+sin^2(theta)=1

Find sine 65 degrees? - August 10th 2010, 06:55 AMEphemerasylumFailed attempt
okay we get started by listing what may be of help here:

;

;

;

with the trigonometric identities:

First we assume

;

therefore we have

,

together with the application of the identities introduced above, which results:

(note that y is less than )

The identities also yield that

Therefore we may find the only real value of y (which isn't easy)

Hence

The bad news is that, I haven't yet figured out how to solve the equation without a calulator. So good luck on that, and I'll put my findings here as soon as I'm getting something. - August 14th 2010, 03:38 PMhelopticor
I think there is not really a nice answer to this problem. GAVREED2, are you sure there's no typo?

- August 14th 2010, 03:49 PMskeeter
see this "second" post ...

http://www.mathhelpforum.com/math-he...le-153405.html