Without using mathematical tables or calculator , show that

satisfies the equation

.

Thanks for ur help .

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- Aug 9th 2009, 01:26 AMthereddevilstrigonometry (1)Without using mathematical tables or calculator , show that

satisfies the equation

.

Thanks for ur help . - Aug 9th 2009, 02:24 AMMoo
Hello,

Consider :

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Remember these identities :

Multiply them :

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Hence

And if , then

So (1)

Now notice that :

and are both in the first quadrant (because )

So and

Hence

And it follows from (1) that if

Looks clear to you ? - Aug 9th 2009, 02:34 AMmr fantastic
- Aug 9th 2009, 03:57 AMthereddevils