If x = a cosθ+ b sinθ and y = b cosθ- a sinθ, then x2 + y2 is equal to

An angle in a semicircle is

A chord of length 16 cm is drawn in a circle of radius 10 cm. The distance of the chord from the centre of the circle is

If pq (p+q) = 1, Then the value of 1/p³q³ -p³-q³ is equal to 

If x² + 1/x² = 2, then the value of x - 1/x is

The price of an article is decreased by 10%. To restore it to its former value, the new price must be increased by :