Transcript Slide 1

Trigonometric Ratios
• Consider the triangle given below.
1. The box in the bottom right corner tells
us that this is a right triangle.
2. The acute angle at the bottom left corner
is labeled as the Greek letter θ.

3. The side opposite the right angle is
called the hypotenuse.
4. We will call the side opposite the angle θ
opposite.
5. We will call the side adjacent to angle θ
adjacent.
hypotenuse
opposite

adjacent
We will use the abbreviations for the sides
as given below.
hyp
opp

adj
Basic Trigonometric Ratios
• The basic trigonometric ratio names are given
below along with their abbreviations. These
need to be memorized.
1. sine θ = sin θ
2. cosine θ = cos θ
3. tanget θ = tan θ
4. cosecant θ = csc θ
5. secant θ = sec θ
6. cotangent θ = cot θ
Basic Trigonometric Ratios
• The basic trigonometric ratios are defined as
ratios of sides of the right triangle. These need
to be memorized.
opp
sin 
hyp
adj
cos 
hyp
opp
tan 
adj
hyp
opp

adj
Basic Trigonometric Ratios
• The basic trigonometric ratios are defined as
ratios of sides of the right triangle. These need
to be memorized.
hyp
csc 
opp
hyp
sec 
adj
adj
cot 
opp
hyp
opp

adj
Note that the triangle can be in many
different positions, and there are two
possible acute angles to reference, as
illustrated by the following.
opp 4
sin 

hyp 5
opp 3
sin 

hyp 5
4 in
3 in


5 in