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Trigonometric expressions in Arduino
Arduino provides 3 basic trigonometric functions: sin(), cos() and tan(). All other trigonometric expressions can be derived from these three functions.
All the three functions take in angle in radians (type float) as the input. They return a double.
For sin() and cos(), the value is between -1 and 1. The value for tan() has no such bounds.
Example
The example code below illustrates the use of these functions −
void setup() {
// put your setup code here, to run once:
Serial.begin(9600);
Serial.println();
float pi = 3.14159;
float angle_deg = 30;
float angle_rad = angle_deg*pi/180;
Serial.println(sin(angle_rad));
Serial.println(cos(angle_rad));
Serial.println(tan(angle_rad));
}
void loop() {
// put your main code here, to run repeatedly:
}Output
The Serial Monitor output is −
sin(30°) =1/2, cos(30°) = sqrt(3)/2 = 0.86602, tan(30°) = 1/sqrt(3) = 0.57735. Thus, the values returned are correct.
It will be interesting to see the values printed for 90 degrees, because, tan(90°) is equal to infinity. Let’s try. The Serial Monitor output for the above code, with 30 replaced with 90 is shown below −
As you can see, it printed 7,88,898.12 for tan(90 degrees), which is a very high number. Also note that our pi was defined only till an accuracy of 5 decimal places. So the input to the function was not exactly 90 degrees, but a value very close to it.
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