HP Prime not Computing Correctly

[Nigel (UK)]

Thanks for the link! But you can work out the area of a circle by integrating from \(0^\circ\) to \(360^\circ\) if you adjust the arc length formula appropriately for degrees. Wikipedia tells me that radian measure probably originated in the 17th or early 18th century (AD). Almost 2000 years before that, Archimedes found that the area of a circle of unit radius lies between 223/71 and 22/7 (again from Wikipedia). He wasn't using radians.

More simply, just draw a circle on squared paper and count the squares. No choice of angle measure needed! I'm sure you're not arguing with this.

So: should \(\pi\) in the argument of a trig function mean that it should be interpreted as radians? Maybe. However, the absence of \(\pi\) certainly doesn't exclude radians. An angle might be estimated by the ratio of two lengths; \(\pi\) won't appear then. Or in an expression like \(\sin(kx-\omega t)\), with numerical values for wave number \(k\) and angular frequency \(\omega\), there is again no \(\pi\).

I think it would be better for the calculator to say "There's a \(\pi\) in your expression - do you want to change to radian mode?" when it notices this, rather than doing it silently. Or, if you asked for \(\sin(160)\) in radian mode, it could say "That's a rather large argument - do you want to change to degree mode?". Might be useful for students, and could be turned off if annoying!

Nigel (UK)