Answer:
Solve the inequality as though it were an equation. The real solutions to the equation become boundary points for the solution to the inequality. Make the boundary points solid circles if the original inequality includes equality; otherwise, make the boundary points open circles.
Step-by-step explanation:
Answer:
Step-by-step explanation:
We know that:
And we want to find:
Remember that there is a trigonometric identity that relates the 
function with the function
Then if this means that:
Finally:
