How to draw a line in the direction of a given angle

code.js

litecanvas()

let cx, cy, px, py, len=200

function resized () {
  cx = CENTERX
  cy = CENTERY
}

function update (dt) {
  if (TAPPING) {
    px = TAPX
    py = TAPY
  }  
}

function draw () {
  cls(0)
  circfill(cx, cy, 32, 5)
  if (px != null) {
    let angle = atan2(py - cy, px - cx)
    line(cx, cy, cx + cos(angle)*len, cy + sin(angle)*len, 4)
  }
}

DEMO
https://litecanvas.js.org?c=eJxVUMGKwjAQvecrZm%2BJW6F03WMPIiJeRMSDHkOaSmAYS5OqVfrvTjZa1tPMe5M3b17QBWs0XbSXSgi0AcwtA9Nn0HBtuKKlsshzIeqOTHBngtZ6d7cVSAUPASyAEhbLzX65O0TYj%2FAohn%2Byrql0sCCrkHSuBrmfb7frzSoRwJ6sZe6QUJ%2FQkdEA8LGsavV1PAC9zFVsXGtqhyjfGX6KDH7Vy4uXf5VAHeLbLsbVdELLPjpoKiRbTl%2FpY3NT6Z0jO%2B7kuN9gzl7%2BKdWE%2FycOmPSOPshZVA989hMGqWQy