asin()

[Math]

double asin(double x);

Description

Returns the principal value of the arc sine of x in radians.

Parameters

x: The angle in radians.

Returns

The principal value of the arc sine of x in radians.

Example Code

The code reads the value of a potentiometer connected to pin IN and place the arc sine to the pin OUT.

void setup() {
    pinLabel(0, "IN");   // set the label of pin 0 to "IN"
    pinLabel(1, "OUT");  // set the label of pin 1 to "OUT"
    pinMode(1, OUTPUT);  // set pin 1 as output
    pinLabel(2, "VCC");  // set the label of pin 2 to "VCC"
    powerPin(2);         // set pin 2 as power pin
    pinLabel(3, "GND");  // set the label of pin 3 to "GND"
    groundPin(3);        // set pin 3 as ground pin
}
void loop() {
    int val = analogRead(0); // read the value of the potentiometer
    double angle = map(val, 0, 1023, 0, 180); // map the value
    double asinVal = asin(angle * PI / 180); // calculate the arc sine
    analogWrite(1, (int)map(val, -PI/2, PI/2, 0, 1024)); // map the value
    delay(100); // delay for 100ms
}

Notes and Warnings

The angle should be in radians. To convert the angle from degrees to radians, multiply the angle by PI / 180.
A domain error occurs if the argument is outside the range [-1, 1]. In this case, the function returns NAN.