Why is acos(1.5) an error? Isn't that just asking how many radians it takes to reach 1.5 degrees around a circle?

Guest Mar 27, 2017

#1**0 **

Why is acos(1.5) an error? Isn't that just asking how many radians it takes to reach 1.5 degrees around a circle?

No it is not asking changing radians to degrees

acos is the same as inverse cos.

It is saying if \(cos\theta =1.5 \text{ then what is }\theta\)

Well the cos of any angle must be between -1 and +1

1.5 is outside this range so the question does not make sense.

If you want to know how many radians in 1.5 degrees then think of it like this

\(360^\circ=2\pi ^c \\ 180^\circ=\pi ^c \\ 1^\circ=(\frac{\pi}{180})^c\\ 1.5^\circ=(\frac{1.5*\pi}{180})^c\\ 1.5\;degrees=\frac{\pi}{120}\;radians\\ \)

Melody
Mar 27, 2017