
#1
Dec204, 08:02 PM

P: 1

Here is my problem: I got A right, but B is wrong... Can point out what I'm doing wrong? Thanks!
Develop a Mathematica procedure to find 5 roots of the following equations. a.) x^5 + 5x^4 + 4x^3 + 3x^2 + 2x + 1 = 0 b.) e^x sin^2 x  cos x = 0 For part A, I got NSolve[x^5 + 5x^4 + 4x^3 + 3x^2 + 2x + 1 == 0, x] And got 5 roots of the following: {{x > 4.19273}, {x > 0.564099  0.390903 \[ImaginaryI]}, {x > 0.564099 + 0.390903 \[ImaginaryI]}, {x > \ 0.160462\[InvisibleSpace]  0.693272 \[ImaginaryI]}, {x > 0.160462\ \[InvisibleSpace] + 0.693272 \[ImaginaryI]}} But for part B, I did the procedure: FindRoot[E^x Sin^2 x  Cos x == 0, x] And gave me: FindRoot::fdss: Search specification x should be a list with a 25 elements. (FindRoot[\[ExponentialE]\^x\ Sin\^2\ x  Cos\ x == 0, x]\) ~TRI~ 



#2
Dec204, 11:55 PM

P: 291

You might also be interested in the TeXForm command if you're going to be posting output from Mathematica much. That way, you only need put in the [ tex ] and [ /tex ] tags.
[tex]\{ \{ {x\rightarrow {2.96732}}\} , \{ {x\rightarrow {0.652083  0.707484\,\imag }}\} , \{ {x\rightarrow {0.652083 + 0.707484\,\imag }}\} , \{ {x\rightarrow {0.135744  0.587885\,\imag }}\} , \{ {x\rightarrow {0.135744 + 0.587885\,\imag }}\} \}[/tex] is output from NSolve[x^5 + 5x^4 + 4x^3 + 3x^2 + 2x + 1 == 0, x] // TeXForm or TeXForm[NSolve[x^5 + 5x^4 + 4x^3 + 3x^2 + 2x + 1 == 0, x]] J 



#3
Dec304, 09:00 AM

P: 60

What you do is replace sin^2(x) by 1cos^2(x) and you get the DE:
e^x cos^2(x) +cos(x)==e^x, using the Solve function on Mathematica, BUT dont solve in terms of x solve for Cos[x] i.e: Solve[e^x cos^2(x) +cos(x)==e^x, Cos[x] ] You then get solutions in terms of Cos[x], which you can then solve trigonometrically, the reason Mathematica doesnt like the equation is because the there are infintite solutions, and the Solve function cant handle these. Hope this helps Ray 


Register to reply 
Related Discussions  
mathematica help.  Math & Science Software  9  
Mathematica 6.0 Changes Everything  Math & Science Software  37  
Mathematica Help  Math & Science Software  5  
Where can I download Mathematica  Math & Science Software  3  
mathematica bug?  Math & Science Software  5 