float $acos_of_t; 

float $cos_of_acos_of_t;

// acos(0) is 90 degrees because cos(90 degrees) = 0

$t                = 0.0;

$acos_of_t        = acos($t);

$cos_of_acos_of_t = cos($acos_of_t);

print("t, acos(t), cos(acos(t)) = " + string($t) + ", " + string($acos_of_t) + ", " + string($cos_of_acos_of_t));

// 1.1 is not a meaningful input into acos and returns NaN 

// (-1.#IND00)

$t                = 1.1;

$acos_of_t        = acos($t);

$cos_of_acos_of_t = cos($acos_of_t);

print("t, acos(t), cos(acos(t)) = " + string($t) + ", " + string($acos_of_t) + ", " + string($cos_of_acos_of_t));