I couldn't solve this IVP problem because I did not memorize the identities of trigonometrics raised to the square. So my procedure was so far good until I couldn't substitute cos^2 (x).
The second problem was about finding the critical values of the function below and I did find them for y=-2, 4 and 7. However, when I tried to sort them by their stability, I couldn't determine any behavior of the function when y>7 because it would give a negative value on the root at the left and end with an undefined value. So I assumed it was a semistable value.
I am just fucking wasted and there are 3 exams left on the semester.