TAN():

TAN(X);

<?Php
echo TAN(PI()); // Output is  0 
echo "<br>";
echo TAN(PI()/2); // Output  is infinity 
echo "<br>";
echo ROUND(TAN(PI()/3),2); // Output is 1.73
echo "<br>";
echo TAN(PI()/4); // Output is 1 
?>

deg2rad() with TAN()

<?Php
echo TAN(deg2rad(0)); // Output  is 0
echo "<br>";
echo TAN(deg2rad(90)); // Output is 1.6331239353195E+16  // same as infinity 
echo "<br>";
echo TAN(deg2rad(180)); // Output  is -1.2246467991474E-16//  same as 0
?>

Plotting of SIN & SIN curves by using PHP GD function with deg2rad()