Question

Help...
Prove that sin36 degrees = sqrt[10 - 2*sqrt(5)]/4

Answer 1

HINT: 180º/5 = 36º

Answer 2

next, what's formula using i do

Answer 3

Seems like it won't help. Try this, using the formula sin (a + b) = cosa sinb + cosb sin a

sin36º = 2 sin18º cos18º = 2 cos72º sin72º

Answer 4

ok, i know that formula..
but i think we get the new problem... because sin/cos 18 or sin/cos 72 not eassy to get.. it's very difficul, right ?

Answer 5

It seems so. Bump your question to get more helps. Maybe someone can help you with this.

Answer 6

ok, thanks...

Answer 7

@cwrw238 , @experimentX , @estudier , @Hero , @Zarkon , @sauravshakya , @all... help me please, how to get it

Answer 8

any idea guys ?

Answer 9

Use quadratic formula