something wierd with sinc function

while using sinc(x) function there is a difference between sinc(x) and sin(x)/x also when i manually calculate its equal to

sinc(1.5)= -0.2 (negative value) sin(1.5)/1.5 = 0.6 (positive value)

why?

Answer 1

[Matt J]

Sounds like you're using a pi-normalized sinc

      >> sin(1.5*pi)/(1.5*pi)

    ans =

       -0.2122

It's a normalization often used so that the roots of the sinc() will be at the integers.