查看完整版本 : 2cosx=3tanx

純情小帥帥 2019-5-23 09:31 PM

2cosx=3tanx

求救
2cosx=3tanx匕土
solve equations 0°smaller or equal to x smaller than 360°

ppresent 2019-5-24 07:50 PM

2cosx=3tanx
2cosx=3(sinx/cosx)
2(cosx)^2=3sinx
2(1-(sinx)^2)=3sinx
2-2(sinx)^2=3sinx
2(sinx)^2+3sinx-2=0

you can then factorize the equation into the form (asinx+b)(csinx+d)=0
And then solve for sinx, because -1<sinx<1 you could screen out one of the solutions.
And then you could solve for x for x between 0 degree to 360 degree.

halola 2019-5-25 04:02 PM

[quote]原帖由 [i]純情小帥帥[/i] 於 2019-5-23 09:31 PM 發表 [url=https://www.discuss.com.hk/redirect.php?goto=findpost&pid=499824370&ptid=28237037][img]https://www.discuss.com.hk/images/common/back.gif[/img][/url]
求救
2cosx=3tanx匕土
solve equations 0°smaller or equal to x smaller than 360° [/quote]


cos x=1/√(1+tan^2 x)
easy to get tan x=±√3/3
x = 30° , 150°

wonghy215 2019-5-26 03:06 PM

2cosx = 3tanx
((2 +sinx)(-1 +2sinx))/(cos^2(x/2) +sin^2(x/2)) = 0
(2 +sinx)(-1 +2sinx) = 0
sinx = 1/2
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查看完整版本: 2cosx=3tanx