echo "asin(1) = ", asin(1) . "<br />";
echo "asin(0) = ", asin(0) . "<br />";
echo "asin(10) = ", asin(10) . "<br />";
echo "asin(0.5) = ", asin(0.5) . "<br />";
/*
run:
asin(1) = 1.5707963267949
asin(0) = 0
asin(10) = NAN
asin(0.5) = 0.5235987755983
*/