Question

what is the meaning of Trigonometric ? Define ?

Answer 1

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Trigonometric ( Trigonometry ) is a branch of mathematics dealing with the relations of the sides and angles of triangles and with the relevant functions of any angles.

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Answer 2

Trigonometry, the branch of mathematics concerned with specific functions of angles and their application to calculations. There are six functions of an angle commonly used in trigonometry. Their names and abbreviations are sine (sin), cosine (cos), tangent (tan), cotangent(cot), secant (sec), and cosecant (csc). These six trigonometric functions in relation to a right triangle are displayed in the figure. For example, the triangle contains an angle A, and the ratio of the side opposite to Aand the side opposite to the right angle (the hypotenuse) is called the sine of A, or sin A; the other trigonometry functions are defined similarly. These functions are properties of the angle Aindependent of the size of the triangle, and calculated values were tabulated for many angles before computers made trigonometry tables obsolete. Trigonometric functions are used in obtaining unknown angles and distances from known or measured angles in geometric figures.

Based on the definitions, various simple relationships exist among the functions. For example, csc A = 1/sin A, sec A = 1/cos A, cot A = 1/tan A, and tan A = sin A/cos A.Encyclopædia Britannica, Inc.

Trigonometry developed from a need to compute angles and distances in such fields as astronomy, mapmaking, surveying, and artillery range finding. Problems involving angles and distances in one plane are covered in plane trigonometry. Applications to similar problems in more than one plane of three-dimensional space are considered in spherical trigonometry.

History Of Trigonometry

Classical trigonometry

The word trigonometry comes from the Greek words trigonon (“triangle”) and metron (“to measure”). Until about the 16th century, trigonometry was chiefly concerned with computing the numerical values of the missing parts of a triangle (or any shape that can be dissected into triangles) when the values of other parts were given. For example, if the lengths of two sides of a triangle and the measure of the enclosed angle are known, the third side and the two remaining angles can be calculated. Such calculations distinguish trigonometry from geometry, which mainly investigates qualitative relations. Of course, this distinction is not always absolute: the Pythagorean theorem, for example, is a statement about the lengths of the three sides in a right triangle and is thus quantitative in nature. Still, in its original form, trigonometry was by and large an offspring of geometry; it was not until the 16th century that the two became separate branches of mathematics.

angle θ (an angle formed by two radii in a circle) and its chord AB (equal to one side of an inscribed triangle) .Encyclopædia Britannica, Inc.

The first major ancient work on trigonometry to reach Europe intact after the Dark Ages was the Almagest by Ptolemy (c. 100–170 CE). He lived in Alexandria, the intellectual centre of the Hellenisticworld, but little else is known about him. Although Ptolemy wrote works on mathematics, geography, and optics, he is chiefly known for the Almagest, a 13-book compendium on astronomy that became the basis for humankind’s world picture until the heliocentric system of Nicolaus Copernicus began to supplant Ptolemy’s geocentric system in the mid-16th century. In order to develop this world picture—the essence of which was a stationary Earth around which the Sun, Moon, and the five known planets move in circular orbits—Ptolemy had to use some elementary trigonometry. Chapters 10 and 11 of the first book of the Almagest deal with the construction of a table of chords, in which the length of a chord in a circle is given as a function of the central angle that subtends it, for angles ranging from 0° to 180° at intervals of one-half degree. This is essentially a table of sines, which can be seen by denoting the radius r, the arc A, and the length of the subtended chord c, to obtain c = 2r sin A/2. Because Ptolemy used the Babylonian sexagesimal numerals and numeral systems (base 60), he did his computations with a standard circle of radius r = 60 units, so that c = 120 sin A/2. Thus, apart from the proportionality factor 120, his was a table of values of sin A/2 and therefore (by doubling the arc) of sin A. With the help of his table Ptolemy improved on existing geodetic measures of the world and refined Hipparchus’s model of the motions of the heavenly bodies.

Constructing a table of chordsBy labeling the central angle A, the radii r, and the chord c in the figure, it can be shown that c = 2r sin (A/2). Hence, a table of values for chords in a circle of fixed radius is also a table of values for the sine of angles (by doubling the arc).Encyclopædia Britannica, Inc.