Positive trigonometric angle with initial and terminal sides labeled.
Claude Irwin Palmer Library of Practical Electricity: Practical Mathematics For Home Study (New York: McGraw-Hill Book Company, Inc., 1919) 397
2400×1789, 180.0 KiB
1024×763, 25.8 KiB
640×477, 15.1 KiB
320×238, 6.9 KiB