When you rotate a rectangle, you might want to find the bounding box that the rotated rectangle is contained in.

The code below will give you the width and height of the bounding box.
/**
* Gets the bounding box dimensions of the rectangle rotated by the angle.
* @param intAngle The angle in degrees about which the rectangle is being rotated, clockwise.
* @param intWidth The width of the rectangle.
* @param intHeight The height of the rectangle.
* @return
*/
function getBoundingBox( $intAngle, $intWidth, $intHeight ) {
$fltRadians = deg2rad( $intAngle );
$intWidthRotated = $intHeight * abs( sin( $fltRadians) ) + $intWidth * abs( cos( $fltRadians ) );
$intHeightRotated = $intHeight * abs( cos( $fltRadians ) ) + $intWidth * abs( sin( $fltRadians ) );
return array( $intWidthRotated, $intHeightRotated );
}