Consider the function
h(x)={asinx,1−cosx,x≤0,x>0.
Which of the following statements about a guarantees that h is continuous at x=0?
a) h is continuous at x=0 only if a=0.
b) h cannot be continuous at x=0 for any real a.
c) h is continuous at x=0 for every real value of a.
d) h is continuous at x=0 only if a=1.