Solve finding all solutions in 0 2 cosx sin2x sinx cosx si
Solve, finding all solutions in [0, 2). cosx sin2x + sinx cosx - sinx = 0
Solution
given equation is cosx sin2x + sinx cosx - sinx = 0
sin2x =2sinx cosx
cosx 2sinx cosx + sinx cosx -sinx=0
now we have sinx in all the terms so take sinx common
sinx [ 2cos^2 x +cosx -1 ] =0
this will be true when
sinx = 0 or [ 2cos^2 x +cosx -1 ] =0
when x =0, or 2cos^2 x +2cosx -cosx -1 =0
or 2cosx (cosx +1) -1 (cosx+1) =0
or (2cosx - 1) (cosx+1) =0
(2cosx - 1) (cosx+1) =0 is true
when
(2cosx - 1) = 0 or (cosx+1) =0
2cosx =1 or cosx =-1
cosx =1/2 or x=
x= /3, 2 -/3 or x=
x=/3 , 5/3 or x=
so the solution set is { 0, /3 , , 5/3}
