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SOLVED Hp Prime - CAS inconsistent derivatives of sin, cos, tan - CR Haeger - 05-29-2014 10:28 AM In CAS I notice now that taking first derivative of sin, cos or tan yields different results if in radians versus degrees mode. In radians mode, d sin(x)/dx gives cos(x) In degrees mode it gives PI * cos(x)/180 I assume these should be consistent and match the result from radians mode? Running 6030 firmware. RE: Hp Prime - CAS inconsistent derivatives of sin, cos, tan - cdecastro - 05-29-2014 10:40 AM 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 RE: Hp Prime - CAS inconsistent derivatives of sin, cos, tan - Tugdual - 05-29-2014 01:20 PM (05-29-2014 10:40 AM)cdecastro Wrote: 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.Correct $$(g\circ f)'=g'\circ f*f'\\ \sin { (a*x)'=cos(a*x)*a } $$ While converting from degree to radian you get the conversion factor $$a=\frac { \pi }{ 180 } $$ RE: SOLVED Hp Prime - CAS inconsistent derivatives of sin, cos, tan - CR Haeger - 05-29-2014 01:22 PM Yes, of course you and the Prime are both correct... I got tripped up as I used to do DERVX in CAS with the 50G and it forced me to switch from deg --> rad. The Prime provides correct answers in either mode. This would seem to be a great feature for Geometry teachers. Thanks again. ps TW: 3, Me: 0 RE: SOLVED Hp Prime - CAS inconsistent derivatives of sin, cos, tan - Tim Wessman - 05-29-2014 01:30 PM I would think it is more 3 to <some much larger number> and not 0... RE: SOLVED Hp Prime - CAS inconsistent derivatives of sin, cos, tan - CR Haeger - 05-29-2014 01:53 PM (05-29-2014 01:30 PM)Tim Wessman Wrote: I would think it is more 3 to <some much larger number> and not 0... Nope - 3-0 (since the new firmware release). However, Im still waiting to hear if there is a way to recover my custom spreadsheet apps content following the upgrade. Id prefer not to retype all this back in. RE: SOLVED Hp Prime - CAS inconsistent derivatives of sin, cos, tan - Michael de Estrada - 05-29-2014 02:11 PM (05-29-2014 01:53 PM)CR Haeger Wrote:(05-29-2014 01:30 PM)Tim Wessman Wrote: I would think it is more 3 to <some much larger number> and not 0... Start typing. RE: SOLVED Hp Prime - CAS inconsistent derivatives of sin, cos, tan - rprosperi - 05-31-2014 01:29 AM (05-29-2014 01:53 PM)CR Haeger Wrote: ...Id prefer not to retype all this back in. (05-29-2014 02:11 PM)Michael de Estrada Wrote: Start typing. Yup! What he said... It got me too. |