Question

If a sin θ - b cos θ = c and , a cos θ + b sin θ = √(a 2 + b2 - c 2 ).prove that sinθ= cosθ or a≤ = b≤

prove that cosA=cosB

How I can remember all sums in my exams n learn all theorems easily 

Prove that the sum of nth term of A.P 1+5+9+......... Is n(2n-1)

What is the nth term of the G.P x+2xy+4xy^2+........?

The sum of n terms of a series for all value of n is n^2+3n. Find the first 3 terms of the series?

Find the sum of 2n terms of the G.P 2-6+18.........?

If -5,p,q,16 are in A.P.find p and q

Q.17and18

Q.11and12

40th and 50th(b)

Plz solve fastly i need that at any cost with in 1hour