For angle values in properties and their corresponding presentation attributes, the angle unit identifier is optional. If you do not the identifier, the angle value is treated as if it is in degrees. If you provide the identifier, the angle unit identifier must be in lowercase.
When you use angles in an SVG attribute, the angle property is defined as deg for degrees, grad for gradians, or rad for radians. In the SVG DOM, angle values are represented by using SVGAngle or SVGAnimatedAngle objects.
Microsoft Developer Network: [Windows Internet Explorer API reference Article]