math
posted by kenji86 .
how can you use the inverse trigonometrical function on calculator to find the value of x in degree for which sinx = 0.4

The arcsin(x), arcsos(x), and arctan(x) functions on a calculator have been designed and programmed to give you the nearest angle to zero.
So if x > 0, no problem, you get the angle in the first quadrant, but if x< 0 both the arcsin and the arctan will give you the negative angle closest to zero.
BTW, to get the arcsin differs from one calculator to another, on mine to do the above I do ..
2nd F
sin
.4
±
=
and get 23.578...
so to get the correct angles I have to know the CAST rule, that is, I have to know where the different trig functions are positive and negative.
I know the sine is negative in III and IV
for III : angle = 180° + 23.578 = 204.578°
for IV : angle = 360°  23.578 = 335.422° 
why exponential model would be more suitable than a linear model. Thanks.