Transcript Section 9.3b

9.3b – Using Trigonometric
Ratios
Definitions of the Day (DODs)
• Trigonometric Ratios (review)
• Angle of Elevation
Def: The Trigonometric Ratios
B
c
a
A
C
b
length of leg opposite A
a
sinesine
of Aof
= an angle is just a number!!
or sin A 
length of hypotenuse
c
length of leg adjacent to A
b
cosine
of A =
or cos A 
cosine
of anlength
angle
is
just
a
number!!
of hypotenuse
c
length of leg opposite A
a
tangent
of A =
or tan A 
tangent
oflength
an angle
is
just
a
number!!
of leg adjacent to A
b
Example
Use your calculator
(change mode to degrees)
1. a) Find: sin 30°
b) Find: cos 88°
c) Find: tan 45°
Example
B
2. Find x:
50
70°
C
x
A
Example
3. Find x:
x
21°
18
Definition: Angle of Elevation
An angle from the horizontal up to a
line of sight.
Example
4. Suppose you are lying on the ground looking up at
a Redwood tree.
If your angle of elevation to the top of the tree is
42° and you are 280 feet from the tree, how tall is
the tree?
Your Turn!!
1. Find x:
x
60°
y
100
2. Find y:
Sentence Frames
1.
The sine of an angle is a __________________.
2.
The cosine of an angle is a ________________.
3.
The tangent of an angle is a _____________ .
4.
If you looked out your bedroom window, at an angle of
elevation of 10°, what would you see?
____________________________________________
____________________________________________