f(x) = sin x - sin x/cos x = sin x*(1 - 1/cos x) = sin x*(cos x - 1)/cos x.f(x)=sinx−sinxcosx=sinx⋅(1−1cosx)=sinx⋅cosx−1cosx.
Solve sin x = 0sinx=0 and (cos x - 1) = 0(cosx−1)=0
Reminder. f(x)f(x) undefined when cos x = 0 --> x = pi/2 and (3pi)/2.cosx=0−→x=π2and3π2.
sin x = 0 --> x = 0; x = pisinx=0−→x=0;x=π; and x = 2pix=2π
cos x - 1 = 0 --> cos x = 1 --> x = 0; and x = 2picosx−1=0−→cosx=1−→x=0;andx=2π
Answers within period (0, 2pi): 0, pi, 2pi(0,2π):0,π,2π.
Check:
x = pi --> f(x) = 0 - 0 = 0x=π−→f(x)=0−0=0 (correct)