Write the equation of the circle with centre (2, −3) and radius 4.

Find the length of the tangent from the point (5, 6) to the circle x² + y² = 9.

Find the equation of the circle passing through the origin with its centre at (3, 4).

Find the centre and radius of the circle x² + y² − 6x + 4y − 12 = 0.

Find the equation of the circle with the points (1, 2) and (5, 6) as the ends of a diameter.

If A = {1, 2} and B = {a, b}, write A × B and state the number of relations from A to B.

Convert 150° into radians and 3π/4 radians into degrees.