Find the roots of the equations:
1.
2.
3.
These are transcendental equations - which means that exact solutions cannot be found except for special cases eg. For 1. and 3. x = 0 is one of the solutions. To get the other solutions you will need to use technology to get decimal approximations of them.
This is only good if either:
1. You don't want very good accuracy in your solutions, or
2. You use technology to draw them and then get that same technology to find the x-coordinates of the intersection points.
You could also leave them in terms of though?
For example would have solutions of where k is an integer
Note this only words if x is in radians, the small angle approximation (what sbcd90 describes) is a truncation of the Taylor series for sin, cos and tan respectively. It works because as x is much less than one it's powers will decrease rapidly.