Define a relation \( R \) on the interval \( \left[0, \frac{\pi}{2}\right) \) by \( x \,R\, y \) if and only if \( \sec^2 x - \tan^2 y = 1 \). Then \( R \) is:
both reflexive and transitive but not symmetric
an equivalence relation
both reflexive and symmetric but not transitive
reflexive but neither symmetric not transitive