Quantitative Aptitude - Arithmetic Ability Questions

What is the value of a-b when a2+b2-6a-6b+18 = 0 ?

What is the value of [(sin x + sin y) (sin x – sin y)]/[(cosx + cosy) (cosy – cosx)]?

2sin[(C+D)/2].sin[(D­-C)/2] is equal to

sin(A+B) -­ sin(A-­B) is equal to

What is the value of equation a3+b3+c3-3abc if a2+b2+c2=ab+bc+ca+4 and a+b+c = 4.

What is the value of Cot 45° + Cosec 60°?

What is the equation of the line perpendicular to the line 5x + 3y = 6 and having Y-intercept -3?

The angle of elevation of the top of a hill at the foot of the tower is 60 deg and the angle of elevation of the top of the tower from the foot of the hill is 30 deg. If the tower is 50 m high, what is the height of the hill?