Mathematical Treasure: De Morgan’s Trigonometry

The British mathematician Augustus De Morgan (1806-1871) was particularly noted as an excellent teacher. All of his texts were written with the learner in mind: De Morgan supplied details and insights tailored especially for the student. De Morgan’s Elements of Trigonometry and Trigonometrical Analysis (1837) provides a good example of this policy.

De Morgan provided a detailed explanation of the basic trigonometric functions as functions.

Using a geometric demonstration, De Morgan “connected” the functions, showing their relationships to each other.

This text was written for future university calculus students. The differentiation of the trigonometric functions is discussed. Note the “operator” form of the derivative.

The images above were obtained through the courtesy of the University of California Libraries. The book may be viewed in its entirety in the Internet Archive.

Index to Mathematical Treasures