the acos funtion will not accept negagive numbers (e.g. -075) . WHY?

>> x = -1:.05:1;
plot(x,acos(x))
grid on
Subscript indices must either be real positive integers or logicals.

Answer 1

[Walter Roberson]

You have either defined a variable named "acos" or a variable named "plot"

[Timothy Goldsmith]

Many thanks. Several seemingly unrelated things generate that error message.