Let f(x)={a(1−cosx)x2x<0bx=0sin(cx)xx>0f(x) = \begin{cases} \frac{a(1 - \cos x)}{x^2} & x < 0 \\ b & x = 0 \\ \frac{\sin(cx)}{x} & x > 0 \end{cases}f(x)=⎩⎨⎧x2a(1−cosx)bxsin(cx)x<0x=0x>0. For fff to be continuous at x=0x=0x=0, which relations must hold?
a2=b=c\frac{a}{2} = b = c2a=b=c
a=b=ca = b = ca=b=c
a=b=c2a = b = \frac{c}{2}a=b=2c
2a=b=c2a = b = c2a=b=c