Run results for: atan2 vs acos

Run details:

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36

Browser: Chrome 81

Operating system: Linux

Device Platform: Desktop

Date tested: one year ago

Test name	Executions per second
acos	1.5 Ops/sec
atan2	4.4 Ops/sec

Script Preparation code:

var N = 1000000;
var x = new Float32Array(N);
var y = new Float32Array(N);

for (var i = 0; i < N; ++i) {
    x[i] = 100 * Math.random();
    y[i] = 100 * Math.random();
}

Tests:

acos
var fn = Math.acos; for (var i = 0; i < N; ++i) { fn(x[i]/Math.sqrt(x[i]*x[i]+y[i]*y[i])); }
atan2
var fn = Math.atan; for (var i = 0; i < N; ++i) { fn(y[i], x[i]); }