Find dy/dx and d2y/dx2. x = 4 sin(t), y = 5 cos(t), 0 < t < 2π dy dx = correct: your answer is correct. d2y dx2 = correct: your answer is correct. for which values of t is the curve concave upward? (enter your answer using interval notation.)

Then it follows that

The curve is concave upward when its second derivative is positive. The numerator is non-negative for all values of , so the denominator determines the sign. is positive for , so is positive for . This means the curve is concave upward when

where is any integer.

where is the figure