Combine two vibrations of equal amplitude and phase difference `90^@`

What is the relation between path difference and phase difference?

Two satellites of equal masses are revolving around at different heights. Will their moment of inertia same or different?

In the circuit show it the figure Find the phase difference between potential differences across C and R2

If two adjacent angles are equal, then each angle measures 90^@ .

What is the distance between the two points which have a phase difference of 2pi ?

Consider a pair of identical pendulums, which oscillate with equal amplitude independently such that when one pendulum is at its extreme position making angle of 2^@ to the right with the vertical, the other pendulum makes and angle of 1^@ to the left of the vertical. What is the phase difference between the pendulums?