Trigonometry is a branch of mathematics that deals with the measurement of angles and the ratio of sides of a right-angled triangle. It is one of the most important branches of mathematics and finds huge application in diverse fields such as astronomy, mapmaking, surveying, and artillery range finding. The word trigonometry comes from the Greek words "trigonon" meaning "triangle" and "metron" meaning "to measure".

Some key concepts in trigonometry include:

• Trigonometric functions: There are six functions of an angle commonly used in trigonometry: sine (sin), cosine (cos), tangent (tan), cotangent (cot), secant (sec), and cosecant (csc) . These functions are properties of the angle independent of the size of the triangle and are used to obtain unknown angles and distances from known or measured angles in geometric figures.

• Right-angled triangle: A right triangle has three sides, which can be uniquely identified as the hypotenuse, adjacent to a given angle, or opposite. The Pythagorean theorem applies to right triangles, which states that the square of the hypotenuse is equal to the sum of the squares of the other two sides.

Trigonometry basics deal with the measurement of angles and problems related to angles. There are three basic functions in trigonometry: sine, cosine, and tangent. These three basic ratios or functions can be used to derive other important trigonometric functions: cotangent, secant, and cosecant. Trigonometry is further classified into two sub-branches: plane trigonometry and spherical trigonometry.

In summary, trigonometry is a branch of mathematics that deals with the measurement of angles and the ratio of sides of a right-angled triangle. It is used to find the measure of unknown dimensions of a right-angled triangle using formulas and identities based on the relationship between the sides and angles of the triangle.