Let a belong to [0,2 π], and the equation x ^ 2sina + y ^ 2cosa = 1 denotes an ellipse with the focus on the X axis, then the value range of a is

Let a belong to [0,2 π], and the equation x ^ 2sina + y ^ 2cosa = 1 denotes an ellipse with the focus on the X axis, then the value range of a is

X ^ 2sina + y ^ 2cosa = 1, that is, x ^ 2 / (1 / Sina) + y ^ 2 / (1 / COSA) = 1 represents an ellipse,
First of all, Sina and cosa should be greater than 0, that is, 0 1 / cosa
So cosa > Sina
So the value range of a is (0, π / 4)

If the equation x ^ 2sina-y ^ 2cosa = 1 for X, y denotes an ellipse, then what is the limit of a
As above Better be more detailed
If it is a hyperbola, is it in the same quadrant

Sina > 0, cosa