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hartnn
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really ?

hartnn
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without calcy ?

hartnn
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first can u find sin 18 without calcy ?

DLS
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noo :/

hartnn
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pretty standard

hartnn
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let x= 18
5x = 90
3x = 902x
now take sin on both sides.

hartnn
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sin 3x = sin(902x)
sin 3x = cos 2x

hartnn
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now put the formula fo sin 3x and cos 2x in terms of powers of sin x only.

hartnn
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u get a cubic in sin x. solve it.

DLS
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wait,theres a formula for sin3x? :P

hartnn
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absolutely.

DLS
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:O

hartnn
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sin 3x = 3sin x  4 sin^3 x

DLS
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okay yes ! i remember :P

DLS
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thanks!

DLS
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okay I guess i can do it now

hartnn
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from sin 18, u get cos 36
from the formula of cos 2x in terms of sin x

hartnn
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good :)

DLS
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:D