# Thread: sol. Of f(x)=tan(0.8*x) + x=0 confuse

1. ## sol. Of f(x)=tan(0.8*x) + x=0 confuse

Dear all
sol. Of f(x)=tan(0.8*x) + x=0 is x= 0 ; 2.448218394 ; by using maple software，but in f(x)_x 2D plot can find another sol. by using matlab software，please help me to understanding which one is correct answer.

Thank u for any help ^^

2. ## Re: sol. Of f(x)=tan(0.8*x) + x=0 confuse

Are you using radians for both?

3. ## Re: sol. Of f(x)=tan(0.8*x) + x=0 confuse

The function f(x) = tan(0.8x) is a discontinuous function that goes from negative infinity to positive infinity in each interval -pi/1.6<x<pi/1.6, pi/1.6<x<3pi/1.6; 3pi/1.6<x<5pi/1.6, etc. Thus there is a solution for tan(0.8x)+x= 0 in each of interval, and hence there are an infinite number of solutions. See the attached plot which shows 5 intervals of the function.

4. ## Re: sol. Of f(x)=tan(0.8*x) + x=0 confuse

thank u for ur answer. ^^