Similarity of any right triangle with the
same acute measure.
 All 3 of the triangles are
similar
 Their sides are in
proportion
 We can write these
proportions differently
Trig Ratios
 Sine of an angle =
Opposite
Hypotenuse
opposite
 Cosine of an angle =
 Tangent of an angle =
hypotenuse
Adjacent
Hypotenuse
Opposite
Adjacent
adjacent
EXAMPLE 1: Write each trig ratio as a fraction and as a
decimal rounded to the nearest hundredth.
a) Sin J
b) Cos J
c) Tan K
d) Sin K
Special Right Triangles
30-60-90
60˚
45-45-90
45˚
45˚
30˚
Sin 30 =
Cos 30 =
Tan 30 =
Sin 60 =
Cos 60 =
Tan 60 =
Sin 45 =
Cos 45 =
Tan 45 =
Calculating Trig Ratios
 Use your calculator to find each trig ratio. Round to
the nearest hundredth. (MAKE SURE YOU ARE IN
DEGREES)
A) Sin 52˚
B) Cos 19˚
C) Tan 65˚
Sine & Cosine Properties
 Sin & Cos of an angles is always less than _____
Solving Trig Equations to Find Missing Lengths
Find BC to the nearest hundredth.
1) Draw your picture
2) Set up a Trig ratio
using what you
have and what you
need.
3) Cross multiply
4) Solve
Find QR to the nearest hundredth.
Find FD to the nearest hundredth
The Pilatusbahn in Switzerland is the world’s steepest cog railway. Its steepest
section makes an angle of about 25.6˚ with the horizontal and rises about 0.9
km. To the nearest hundredth of a kilometer, how long is this section of the
railway track?
Assignment #2
 Page 529 #’s 1-21,(82)