rad_to_deg function not working?

[danmarek]

I am trying to create a formula in a quiz on refraction.  Every step of my formula is correct until I add the rad_to_deg() to get the final answer in degrees and not radians (I'm a physics teacher, not a mathematician).  When I remove that from the formula I get the correct answer in radians but I can't get it to convert to degrees.  Am I doing something wrong or is this a bug?  Any advise? 

 

[Draco]

Hi, I'm a fellow physics instructor; this looks like Snell's Law for air and some random material, and by all accounts the formula seems correct. I ran into problems like this making bottomless javascript practice using random numbers and never figured out a solution. Interestingly enough:

Works: deg_to_rad(asin(n*sin(deg_to_rad(x)))) but air is denominator

Doesn't work: deg_to_rad(asin(1/n*sin(deg_to_rad(x)))) in any algebraic form w/ or w/out parentheses

Works: asin(1/n*sin(deg_to_rad(x)))   but answer in radians

Workaround: asin(n1/n2*sin(deg_to_rad(x)))*180/pi()   generalized for materials other than air

Some of the issues I came across, were that I had to specify a value to be numeric in javascript to get some things to work. We can't do that here, but luckily the workaround is a similar number of characters to the actual string so it's not burdensome. However issues could arise with this in more complex formulas. I've duly noted more of Canvas' limitations.