Triangles and Sectors in Quadrant I
Illustration of an angle &alpha with the vertex at the center, O, of a circle with radius OB. AC and BD are perpendicular to OB and join B with C. The are of the triangle OBC is less than the are of the sector OBC, and the sector OBC is less than the triangle OBD.
Keywordssector, tangent, angle, triangles, Sine, Tan, acute, trigonometry, sin, cos, cosine, trigonometric, trig functions, reference, quadrant 1
George N. Bauer, PH.D. and W.E. Brooke, C.E., M.A. Plane And Spherical Trigonometry (Boston: D.C. Heath & Co., 1917) 121