Question

Solve the equation `cosx(cosx+2)=0` in the interval `0^@ <= x <= 360^@`?

Answer 1

`x=(90^@,270^@)`

Explanation:

As we have `cosx(cosx+2)=0`

and as range of `cosx` is `[-1,1]` and hence `cosx+2>=1` and `cosx+2!=0`

We can only have `cosx=0` and as such in the interval `(0,360)`

`x=(90^@,270^@)`

Answer 2

`x=90^@,x=270^@`

Explanation:

`"equate each factor to zero and solve for x"`

`cosx=0rArrx=90^@,x=270^@`

`cosx+2=0rArrttcosx=-2larrcolor(red)"no solution"`

`rArrx=90^@" or "x=270^@to(0,360)`