Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

You are not logged in.

#1 2019-05-24 11:15:25

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.

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.

Offline

#2 2019-05-24 23:11:39

ganesh
Registered: 2005-06-28
Posts: 31,672

Re: tan(18°)

Hi,

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

It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Offline

#3 2019-05-24 23:17:16

Jaspers
Member
Registered: 2019-05-24
Posts: 54

Re: tan(18°)

Can you move this thread to that section? Thanks.

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.

Offline

#4 2019-05-25 23:27:54

Bob
Registered: 2010-06-20
Posts: 8,913

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

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

Offline

#5 2019-05-26 04:42:49

Jaspers
Member
Registered: 2019-05-24
Posts: 54

Re: tan(18°)

Thanks Bob!

My solution is entirely non-geometric.

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.

Offline