【實用教育app】FuncXY|最夯免費app

FuncXY is an application to plot 3D graphs of functions of two variables x and y. You can enter the formula for the function you want to plot. This must be an expression in no variables other than x and y, and the usual arithmetical operators + - * / and ^ (for exponentiation). You can add parentheses in the usual way. Blank spaces are allowed. The minimum and maximum values of x and y, as well as the step sizes, must be supplied, in the same format as given in the default example. If function values are too high or too low to be reasonably visualized, the expression is not accepted, nor is it in the case of division by zero, and, obviously, if there are any syntax errors. As you enter a formula, it is displayed in more readable notation just above the text you are entering or editing.

The function surface can be viewed from any viewpoint. There are buttons to change the viewpoint: down, up, left, right, and far and near. The latter two apply to the distance between the viewpoint and the object. As usual, the back button causes the previous screen, with the function expression to appear again, so the expression can be modified.

You can also specify the viewing direction by entering two angles (often denoted by phi and theta): one is the angle between the z-axis and the line of sight, the other is the angle between the projection of that line onto the xy-plane and the positive x-axis.

The following functions, well-known in mathematics or programming, are supported:

abs, floor, ceil, exp, log, max, min, sin, cos, tan, asin, acos, atan, sqrt. You can also use the constant pi (or PI).

Arguments must be surrounded by parentheses: sin(x), not sin x.

As usual, max and min take two arguments, the others take one. Note the restricted domains of some of these functions:

log(x): x positive

tan(x): x not equal to pi/2 (plus any multiple of pi)

asin(x), acos(x): x between -1 and +1 (inclusive)

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