如何平移一个矩形，始终包围另一个矩形？

既然旋转角度相同，那两个矩形就是轴对齐的，只需要判断内部矩形的坐标即可，不需要什么数学知识😈补充一个简单的例子:

  const canvas = document.createElement('canvas');
  document.body.appendChild(canvas);
  const box = {x:100, y:25, width:100, height:100, rotation:0};
  const rect = {x:0, y:0, width:50, height:50}
  const ctx = canvas.getContext('2d');
  const globalToLocal =  (x, y) => {
    const cx = box.x + box.width / 2
    const cy = box.y+ box.height/ 2
    const dx = x - cx
    const dy = y - cy
    const cos = Math.cos(box.rotation)
    const sin = Math.sin(box.rotation)
    const rx = dx * cos + dy * sin
    const ry = -dx * sin + dy * cos
    return { x: rx + cx - box.x, y: ry + cy - box.y }
  }
  canvas.onmousemove = (e) => {
    let {x, y} =  globalToLocal(e.offsetX, e.offsetY)
    x -= rect.width/2
    y -=rect.height/2
    if (x < 0) x = 0
    if (x > box.width - rect.width) x = box.width - rect.width
    if (y < 0) y = 0
    if (y > box.height - rect.height) y = box.height - rect.height
    rect.x = x
    rect.y = y
  }
  
  const loop = () => {
    box.rotation += 0.001;
    ctx.resetTransform();
    ctx.clearRect(0, 0, canvas.width, canvas.height);
    ctx.translate(box.x +box.width/2,box.y +box.height/2);
    ctx.rotate(box.rotation);
    ctx.strokeStyle = "red"
    ctx.strokeRect(-box.width/2, -box.height/2, box.width, box.height)
    ctx.strokeStyle = "blue"
    ctx.translate(-box.width/2,  -box.height/2);
    ctx.strokeRect(rect.x, rect.y, rect.width, rect.height)
    requestAnimationFrame(loop);
  }

  requestAnimationFrame(loop);