Trigonometry problem

  • #1
This is not homework question, just curious about it though. This problem is supposed to be done without a computing device and was in an exam at a university course. I don't think it can be done.

Homework Statement


I want to find the maximum of this function:

Y = sin(x) + sin(2x)

Homework Equations





The Attempt at a Solution



Attempted sin(2x) = 2sinx*cosx, tried to draw it, tried to go euler's formula, no luck whatsoever (of course I take the derivative!)

Mathematica gives me this:

FindMaximum[Sin[x] + Sin[2*x], {x, 0}]

Out[1]= {1.76017, {x -> 0.935929}}

Any ideas? It really seems simple, but I just can't figure it out...

Thanks!
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
6,230
31
Why don't you just solve dy/dx = 0 and then sub cos(2x) as 2cos2-1 ?

You should get a quadratic in cosx to solve.
 
  • #3
Why don't you just solve dy/dx = 0 and then sub cos(2x) as 2cos2-1 ?

You should get a quadratic in cosx to solve.
Lol where is my mind! Thanks :P
 

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