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- Sep 24th 2011, 03:15 AMafrim1Calculate tan^2(36) tan^2(72)
- Sep 24th 2011, 07:46 AMsbhatnagarRe: Calculate tan^2(36) tan^2(72)
The Problem is very easy.

http://latex.codecogs.com/gif.latex?...18\cot^{2}18=1 - Sep 24th 2011, 08:31 AMafrim1Re: Calculate tan^2(36) tan^2(72)
no I know this is easy

but

- Sep 24th 2011, 08:46 AMsbhatnagarRe: Calculate tan^2(36) tan^2(72)
Okay sorry I read

also,

Therefore - Sep 24th 2011, 09:19 AMafrim1Re: Calculate tan^2(36) tan^2(72)
hahah very quickly I dont understad where you get worth of tan^2(36) tan^(72) can you explain

- Sep 24th 2011, 11:30 AMHallsofIvyRe: Calculate tan^2(36) tan^2(72)
He

**multiplied**! .

Now, if you are asking**how**sbhatnagar determined that , that's a really good question! Come on, sbhatnagar, let us in on the secret. - Sep 25th 2011, 02:34 AMafrim1Re: Calculate tan^2(36) tan^2(72)
yes

- Sep 25th 2011, 05:27 AMpiscoauRe: Calculate tan^2(36) tan^2(72)
triple angle formula can be used to find the exact value of tan 36 and tan 72.(Happy)

- Sep 25th 2011, 05:43 PMmr fantasticRe: Calculate tan^2(36) tan^2(72)
- Oct 6th 2011, 02:42 AMsbhatnagarRe: Calculate tan^2(36) tan^2(72)
To find sin(72):

Let x = 18

So now using quadratic formula,

Now use sin^(2)x+cos^(2)x=1 to find cos(x)

Now you have,

Therefore

- Oct 11th 2011, 05:26 AMsbhatnagarRe: Calculate tan^2(36) tan^2(72)
If then and

Therefore

The value of sin(36 degrees) can be found by using the formula of sin(2x).

- Oct 11th 2011, 06:57 AMBookEnquiryRe: Calculate tan^2(36) tan^2(72)
ha ha I searched a lot of similar crazy expressions. It seems difficult to learn all of them.

Exact trigonometric constants - Wikipedia, the free encyclopedia

Trigonometry Angles -- from Wolfram MathWorld - Oct 11th 2011, 07:06 AMBookEnquirywrong reply