Question

Question #13bca

Answer 1

If we re-write the equation with `x=\pi` we get `1+cos(-\pi)=0`. By subtracting 1 from both sides we find that, for this to be true, `cos(-\pi)=-1` must be true. And the cosine of `-\pi` radians is indeed equal to `-1`.

Explanation:

The key is realising that the angle needs to be expressed in radians, not degrees.