Your calculator is using Degrees. sin() uses Radians. (As is explained in the reference page.)
float answer = sin(140.0);
Serial.println(answer);
Returns 0.98. My calculator, in Radians-mode, returns the same thing.
If I assume you mean "140 degrees" then converting to radian:
float answer = sin(140.0*(3.14/180.0));
Serial.println(answer);
Returns 0.64.
Also note that my integers are in float/decimal. "140.0" instead of "140".