Math Is Fun Forum

Jaspers

Member

Registered: 2019-05-24

Posts: 54

tan(18°)

Without using a calculator, prove that

No calculators, please. Well, you can’t use a calculator anyway; that value is irrational so a calculator won’t give you the exact result.

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Reason is like an open secret that can become known to anyone at any time; it is the quiet space into which everyone can enter through his own thought.

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,410

Re: tan(18°)

Hi,

Are you posting a puzzle? You ought to post in 'Games and Puzzles' topic, not 'Help me' topic.

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It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

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Jaspers

Member

Registered: 2019-05-24

Posts: 54

Re: tan(18°)

Can you move this thread to that section? Thanks.

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Reason is like an open secret that can become known to anyone at any time; it is the quiet space into which everyone can enter through his own thought.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,621

Re: tan(18°)

hi Jaspers

Welcome to the forum.

Nice problem.  Had an idea but kept messing up the algebra.  Here's my final version:

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

Jaspers

Member

Registered: 2019-05-24

Posts: 54

Re: tan(18°)

Thanks Bob!

My solution is entirely non-geometric.

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Reason is like an open secret that can become known to anyone at any time; it is the quiet space into which everyone can enter through his own thought.