2. Trigonometry is derived from Greek words
trigonon (three angles) and metron ( measure).
Trigonometry is the branch of mathematics
which deals with triangles, particularly triangles
in a plane where one angle of the triangle is 90
Triangles on a sphere are also studied, in
Trigonometry specifically deals with the
relationships between the sides and the angles of
triangles, that is, on the trigonometric functions,
and with calculations based on these functions.
3. Right Triangle
A triangle in which one angle
is equal to 90° is called right
The side opposite to the right
angle is known as hypotenuse.
AB is the hypotenuse
The other two sides are
known as legs.
AC and BC are the legs
Trigonometry deals with Right Triangles
4. Pythagoras Theorem
In any right triangle, the area of the square whose
side is the hypotenuse is equal to the sum of areas of
the squares whose sides are the two legs.
In the figure
Trigonometry is the branch of mathematics that looks
at the relationship between the length of the sides
and the angles in a right angled triangle.
It helps us calculate the length of unknown sides,
without drawing the triangle, and it also helps us
calculate the size of an unknown angle without having
to measure it.
Let us look at a right angle triangle.
Values of Trigonometric function
0 30 45 60 90
Sine 0 0.5 1/√2 √3/2 1
Cosine 1 √3/2 1/√2 0.5 0
Tangent 0 1/ √3 1 √3 Not defined
Cosecant Not defined 2 √2 2/ √3 1
Secant 1 2/ √3 √2 2 Not defined
Cotangent Not defined √3 1 1/ √3 0