An apparatus for displaying or measuring a trigonometric sine or cosine is provided, which includes a planar surface with a circle or a portion thereof and a bisecting line through the center of the circle. Two arms are attached to the apparatus. The circle, bisecting line and second arm include incremental markings that correspond to the degree and/or radian measurements of the unit circle, trigonometric cosine and trigonometric sine, respectively. A method is also provided which includes rotating one of the arms to a position along the circle to form an angle. Based upon the position of the first and second arms the trigonometric cosine and trigonometric sine of the angle can be read. An electronic display device that displays the trigonometric sine and trigonometric cosine of an angle can also be included.