# Triangles and Sectors in Quadrant I

## Description

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.

## Keywords

acute, angle, cos, cosine, quadrant 1, reference, sector, sin, Sine, Tan, tangent, triangles, trig functions, trigonometric, trigonometry

## Galleries

## Source:

George N. Bauer, PH.D. and W.E. Brooke, C.E., M.A. *Plane And Spherical Trigonometry* (Boston: D.C. Heath & Co., 1917) 121

Courtesy the private collection of Roy Winkelman