Solve a quadratic with trigonometric values in degrees

01282020, 09:57 AM
Post: #9




RE: Solve a quadratic with trigonometric values in degrees
(01282020 05:51 AM)Mark Hardman Wrote: Most of that work could be eliminated if the OP recognized that cos(30) = √3/2. From there, it is only a minor mental effort to come up with d = 2500/(3*9.81). Why on earth would you need a CAS to solve that? Same with OP Let t = tan(x), the equation is just quadratics: 16.1*225*(1+t²) + 800*15*t = 2000 Remember that t = tan(x) have period of Pi = 180°, x have 4 solutions d*cos(30) = 25*sqrt(d/9.81) is also a quadratics (of √d), d thus have 2 solutions. 

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