Question

cos^3(theta)-4cos(theta)=0 find solutions in (0,2pi]

Answer 1

cos(theta)*(cos^2(theta)-4)=0
cos(theta)=0
and
cos^2(theta)=4

Answer 2

cos(theat)=-2
cos(theta)=2
both of these happen
just solve cos(theta)=0

Answer 3

ok?

Answer 4

so its just pi/2 and 3pi/2?

Answer 5

yes cos(pi/2)=0
and cos(3pi/2)=0

Answer 6

and ignore the cos(theta)=2?

Answer 7

how can it be 2
when cos(x) stays between -1 and 1?