please give me just an idea

[fatemeh8989]

hi every body..!!!please give me just an idea and i'll do it myself...i want to prove that the function sin(x) is continious every where in real plane.i already used the difinition of limits and tryed to find a delta according to epcilon...but i think i should use an else tool to go on... i don't know what is it...please help methank you

 

[fatemeh8989]

thank you every one... i solved it...
the key is this formula: sinx - sina = 2 sin ((x-a)/2 )cos((x+a)/2)
good luck