How to plot a log normal distribution function

[ptc-3212469]

Dear all, I desire to plot a probability density function of log normal distribution: f(x)=(1/sqrt(2*pi)*beta*x)exp(-ln(x/M)^2/2*beta^2) on Mathcad but Mathcad announced a yellow message "this variable or function is not defined above". I do not know at which point I am wrong, please help me to figure out. Thanks so much

[StuartBruff]

"Lam Bao" wrote:

Dear all, I desire to plot a probability density function of log normal distribution: f(x)=(1/sqrt(2*pi)*beta*x)exp(-ln(x/M)^2/2*beta^2) on Mathcad but Mathcad announced a yellow message "this variable or function is not defined above". I do not know at which point I am wrong, please help me to figure out. Thanks so much

[ptc-3212469]

Hi Stuart, Thanks for your reply, I figured out. It was a typo error I did. A point automatically appeared when I typed the formule. However, I have another question relating to inverse trigonometric function asin, it seems to return a weird result. For example, I want to calculate sinus of 1.7 radian, I typed on the worksheet sin(1.7) and Mathcad return the value 0.992. To verify the radian of an angle whose sinus is 0.992, I typed asin(0.992) while expecting Mathcad will return 1.7 but no, it returns 1.444 instead. Could you tell me what's wrong with my handling? How I can solve it Thanks very much

[RichardJ]

asin returns the principle value. It has no way to know which of the infinite number of possible angles you had in mind. 1.7 radians is 97.4 deg. 1.44 radians is 82.6 deg. The sin of both angles is 0.992. Richard

[ptc-3212469]

Thanks Richard, I understand, do you know how I can determine the range of the desired angle, for example, I only want Mathcad return the angle in the range of 0 to pi/2. Thank you very much

[TomGutman]

THe principle value for asin is between -pi/2 and pi/2. If you want between 0 and pi/2 you need to use arguments between zero and one. Note that in your original question you started with an angle larger than pi/2, and asin will never return such an angle.