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ACADEMIC

TRIGONOMETRY.

PLANE AND SPHERICAL.

BY

T. M. BLAKSLEE, PH.D. (YALE),

PROFESSOR OF MATHEMATICS IN THE UNIVERSITY OF DES MOINES.

BOSTON:
PUBLISHED BY GINN & COMPANY.
1888.

Educ T168.88.216

MOST LEN L. WENT WORTH

Ser 1941

Entered, according to Act of Congress, in the year 1887, by
T. M. BLAKSLEE,

in the Office of the Librarian of Congress, at Washington.

TYPOGRAPHY BY J. S. CUSHING & Co., Boston.

PRESSWORK BY GINN & Co., BOSTON.

PREFACE.

THE purpose of this arrangement is to aid the memory

by noting analogies.

and a have as spherical analogies x and cos a. Page 12 has page 13, and each "Law" has its analogy.

In Spherical Trigonometry we note the determining groups: side, +, co. function, and ≤,

function.

It is hoped that the Introduction will fix the characteristics of Trigonometry.

This should be accompanied by practical work, and Occupy at least a week.

DES MOINES, IA.

T. M. BLAKSLEE.

NOTE. It is convenient for examinations to have tables separate from formulas.

The explanation of the use of tables should be with them.

Two pages of model solutions and answers may be added. (Opinions asked on this point.)

INTRODUCTION.

DEF. Trigonometry is, etymologically, the Science of Measuring Triangles. Besides this, it now includes the Science of Angular Functions.

We first inquire, What is a function? then, What are the angular functions?

A function of a variable is a second variable so related to the first that any change in the variable produces a change in the function.

ILL. Oil in lamp and time it has burnt.

DEF. The functions of the angle between two straight lines are the six ratios of the sides of the right triangle formed by these lines and a perpendicular upon one of them from a point in the other.

NOTATION. h, hypotenuse; o, opposite; a, adjacent.

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