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#### Olinguito

##### Well-known member

- Apr 22, 2018

- 251

Prove that

$$\tan18^\circ\ =\ \sqrt{1-\dfrac2{\sqrt5}}.$$

No calculator, computer program, Excel, Google, or any other kind of cheating tool allowed.

Have fun!

$$\tan18^\circ\ =\ \sqrt{1-\dfrac2{\sqrt5}}.$$

No calculator, computer program, Excel, Google, or any other kind of cheating tool allowed.

Have fun!

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