Excerpt from Plane and Spherical Trigonometry: With Stereographic Projections

It is the aim of the authors in this text to teach logarithmic computation along with the principles of trigonometry. Many students gain some knowledge of the theory of logarithms, but few appreciate their value as a labor-saver in computing. In engineering schools, especially, it is complained that students after their study of logarithms are unable to compute with them in courses in professional subjects. The authors feel that the course in trigonometry, with its excellent opportunities for logarithmic computation, is the place to remedy this weakness. With this idea in mind, logarithmic computation has been developed gradually and extended over the entire book. Plenty of problems of a varied character have been supplied for practice and illustration. The importance, in acquiring speed and accuracy, of systematic arrangement of work and of making out a form for the computation in advance before opening tables, is persistently emphasized.

Chapter I is devoted to explaining the theory of logarithms and to numerical computations - including the evaluation of exponential expressions - involving only the use of the table of Logarithms of Numbers. In succeeding chapters, along with the theoretical trigonometry, the other logarithmic tables are introduced and discussed as opportunity arises for their use.

The functions are denned for the general angle. The variations of the functions and their graphs are carefully discussed. In connection with the derivation of the formulae a large number of identities and transformations are given for drill purposes.

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