Name: ____________________ Date: _______________ Block#: _____________
Intro to Trig Ratios
We just looked at how we can determine when a triangle’s side is adjacent, opposite, or the
hypotenuse…now we can use these terms to discover what the ratios of sine, cosine, and tangent
mean in right triangles!
1. Using the triangles drawn here, determine the sine (opposite/hypotenuse), cosine
(adjacent/hypotenuse) and tangent (opposite/adjacent ). Assume all are 3-4-5.
A
B
3
5
C
6
10
Θ
9
15
Θ
4
Θ
8
12
Triangle Opposite Adjacent hypotenuse Ratio
Ratio
side
side
Opp/hypo Adj/Hypo
A
B
C
Ratio
Opp/Adj
Now to use what we know about right isosceles triangles! Assume all pictures are 45-45-90.
D
E
2
5
2
Triangle
D
E
F
F
Opposite
side
10
5
Adjacent
side
10
hypotenuse
Ratio
Opp/hypo
Ratio
Adj/Hypo
Ratio
Opp/Adj