Encyclopedia of Trigonometry.pdf

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Encyclopedia of Trigonometry
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First Edition, 2007
ISBN 978 81 89940 01 0
© All rights reserved.
Published by:
Global Media
1819, Bhagirath Palace,
Chandni Chowk, Delhi-110 006
Email: globalmedia@dkpd.com
Trigonometry
Introduction
Trigonometery is the study of triangles. “Tri” is Ancient Greek word for three,
“gon” means side, “metry” measurementtogether they make “measuring
three sides”. If you know some facts about a triangle, such as the lengths of
it sides, then using trignometry you can find out other facts about that
triangleits area, its angles, its center, the size of the largest circle that can be
drawn inside it. As a consequencethe Ancient Greeks were able to use
trigonometery to calculate the distance from the Earth to the Moon.
Trigonometry starts by examining a particularly simplified trianglethe right-
angle triangle. More complex triangles can be built by joining right-angle
triangles together. More complex shapes, such as squares, hexagons, circles
and ellipses can be constructed from two or more triangles. Ultimately, the
universe we live in, can be mapped through the use of triangles.
Trigonometry is an important, fundamental step in your mathematical
education. From the seemingly simple shape, the right triangle, we gain tools
and insight that help us in further practical as well as theoretical endeavors.
The subtle mathematical relationships between the right triangle, the circle,
the sine wave, and the exponential curve can only be fully understood with a
firm basis in trigonometry.
Trigonometry is a system of mathematics, based generally on circles and
triangles, that is used to solve complex problems (again, mainly involving
circles and triangles). Extensions of various algebraic formulas, namely the
Pythagorean theorem, are utilized.
In Review
Here are some useful formulas that should be learned before delving into
trigonometry:
Pythagorean Theorem a 2 + b 2 = c 2 , in a right triangle where a and b are the two sides,
and c is the hypotenuse.
Pythagorean Triples3-4-5 (the two smaller values being the sides, with the larger the
hypotenuse), 5-12-13, 7-24-25, 8-15-17, and any multiples of these (including 6-8-10,
10-24-26, etc.)
Properties of Special Right Triangles
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In a 45-45-90 right triangle, i.e., an isosceles right triangle, let one leg be x.
The hypotenuse is then x In a 30-60-90 right triangle, let the short leg,
i.e. the leg opposite the 30° angle, be x. The hypotenuse is then equal to 2x
and the longer leg, i.e. the leg opposite the 60° angle, is equal to x* .
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