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Re: Simple problem for math wiz
*To*: mathgroup at christensen.cybernetics.net
*Subject*: [mg1767] Re: [mg1685] Simple problem for math wiz
*From*: Allan Hayes <hay at haystack.demon.co.uk>
*Date*: Wed, 26 Jul 1995 00:53:46 -0400
REVEAL <nomail at me.net> in
[mg1685] Simple problem for math wiz
asks
> Anyone here know how to find the solution set to: sin^2x+sinx-1=0
? > the trick, that is?
> (limited to trig & algebra)
Solve[Sin[x]^2 + Sin[x] - 1 == 0,x]
Solve::ifun: Warning: Inverse functions are being used by
Solve, so some solutions may not be found.
-1 - Sqrt[5] -1 + Sqrt[5]
{{x -> ArcSin[------------]}, {x -> ArcSin[------------]}}
2 2
Although, as Porfirio Beltran observed in [mg1708],
Solve[Sin[x]^2 + Sin[x] - 1 == 0]
-1 - Sqrt[5] -1 + Sqrt[5]
{{Sin[x] -> ------------}, {Sin[x] -> ------------}}
2 2
For the copmplete solution you need to add multiples of 2Pi.
Allan Hayes
De Montfort University, Leicester
hay at haystack.demon.co.uk
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