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# zeros of bessel equation

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 ghasem007 (Electrical) 24 Feb 12 16:27
 hi...I have a matlab question.I want find all of zeros below equation:εr*t0*besseli(1,tp*a)*besselk(0,t0*a)+tp*besselk(1 ,t0*a)*besseli(0,tp*a)=0where:tp=√(k^2-εr*k0^2) t0=√(k^2-k0^2) k0=ω/c. c is light velocity,a,ω,εr,k0 are constant and known.t0 and tp are in terms of k.besseli and besselk are modified bessel functions of first and second type.in above equation all of quantities are known except k that k is zero of equation.i want to find zeros of "er*t0*besseli(1,tp*a)*besselk(0,t0*a)+tp*besselk( 1,t0*a)*besseli(0,tp*a)=0",i.e i want find values of k.by using of solve command only one of the zeros are found.i can not use from fzero command,because there isn't guess point that is imaginary(k)=0.i don't now how find all of zeros in equation.this equation is dispersion relation of plasma.does anyone an idea for find zeros this equation?please help me!
 cloa (Petroleum) 22 Apr 12 4:03
 How about trying a mathematics forum likehttp://mathhelpforum.com/
 hacksaw (Mechanical) 23 Apr 12 13:10
 as a start you can plot the absolute value of your functional with k=x+jy and(x,y) as your coordinates, believe you'll see the answer directly

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