SOLVED Hp Prime - CAS inconsistent derivatives of sin, cos, tan

[cdecastro]

This is correct. The derivative rules d(sin(x))=cos(x) etc.. only hold when the angle is measured in radians. If the angle is in degrees the appropriate rule is found by applying the chain rule.

i.e. if the given angle x is measured in radians as x_rad and in degrees as x_deg, then x_deg = 180/Pi * x_rad, so

d( sin( Pi/180 * x_deg ) ) = cos( Pi/180 * x_deg ) * Pi/180 (using chain rule)
= cos( Pi/180 * x_deg) * Pi/180

Regards,
Chris