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Argonx16
 2 years ago
Best ResponseYou've already chosen the best response.1Take a calculator, and hit the "sin" button and type 18 in. You (may) need a scientific/graphing/google calculator. If you are asking how to do so by hand, I am not qualified to tell you.

AravindG
 2 years ago
Best ResponseYou've already chosen the best response.0there must be a method using the formulas

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.0all I got is the fact that we can write this as\[\sin(\frac\pi{10})\]thinking if we can go somewhere from there...

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.0looking at some way to write this such that we can apply an identity to it...

SUROJ
 2 years ago
Best ResponseYou've already chosen the best response.3http://answers.yahoo.com/question/index?qid=20061025091609AASJNUn

TuringTest
 2 years ago
Best ResponseYou've already chosen the best response.0why is \[\sin(3x)=\cos(2x)\]?

SUROJ
 2 years ago
Best ResponseYou've already chosen the best response.3Most of peoples are not smart....they are clever

campbell_st
 2 years ago
Best ResponseYou've already chosen the best response.0use the power series expansion \[\sin(x) = x/1!  x^3/3! + x^5/5! x^7/7!.....\]

AravindG
 2 years ago
Best ResponseYou've already chosen the best response.0Another way to do this is to start with a regular pentagon where the length of each side is one unit. I'll outline the steps. (You can fill in the details.) Call the pentagon ABCDE. Draw diagonals AC and BE, which intersect at point F. Using the fact that each angle of the pentagon is 108 degrees, you can prove the triangles BFC and AFE are isosceles. Therefore the lengths of line segments CF and EF are also 1 unit. Also note the angles for the triangles are 727236. Now show that ABF and CAB are similar triangles. Since they are similar, this means BE/AB = AB/BF. Since BE = EF + BF, substitute to get (EF + BF)/AB = AB/BF. Let's define x to be the length of BF. Then, since EF = 1, the equation becomes (1 + x)/1 = 1/x, or x^2 + x  1 = 0. Use the quadratic equation to get x = (sqrt(5)  1) / 2. Finally, let's create an 187290 by drawing the altitude of triangle BFC from vertex C to side BF. Since BC = FC, the altitude hits BF at the midpoint of BF, which we will call point G. So, (a) triangle GBE is an 187290 triangle, (b) BG = BF/2 = x/2. Using this 187290 triangle, sin 18 degrees = BG / BC = x/2. Therefore sin 18 = (sqrt(5)  1) / 4.

AravindG
 2 years ago
Best ResponseYou've already chosen the best response.0campbell pls tell ur method
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