Transcript Document

TF.02.5 - Linear Trigonometric
Equations
MCR3U - Santowski
1
(A) Review
We have two key triangles to work with in
terms of determining our related acute angles
and we can place a related acute angle into
any quadrant and then use the CAST “rule” to
determine the sign on the trigonometric ratio
The key first quadrant angles we know how
to work with are 0°, 30°, 45°, 60°, and 90°
2
(A) Review
The two triangles and the CAST “rule” are as follows:
45°
30°
2
1
S
sqr(3)
A
60°
1
sqr(2)
45°
1
T
C
3
(A) Review
We can set up a table to review the key first quadrant ratios:

Sin()
Cos() Tan()
0
0
1
0
30° or /6 ½
3/2
1/3
45° or /4 1/2
1/2
1
60° or /3 3/2
½
3
90° or /2 1
0
Undef.
4
(B) Solving Linear
Trigonometric Equations
We will outline a process by which we
come up with the solution to a
trigonometric equation  it is
important you understand WHY we
carry out these steps, rather than
simply memorizing them and simply
repeating them on a test of quiz
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(B) Solving Linear
Trigonometric Equations
Work with the example of sin() = -½
Step 1: determine the related acute angle
(RAA) from your knowledge of the two
triangles (in this case, simply work with the
ratio of ½)   = 30° or /6
Step 2: consider the sign on the ratio (-ve in
this case) and so therefore decide in what
quadrant the angle must lie  quad. III or IV
in this example
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(B) Solving Linear
Trigonometric Equations
Step 3: draw a diagram showing the
related acute in the appropriate
quadrants
Step 4: from the diagram
determine the principle
angles  240° and 300°
60°
or 4/3 and 5/3 rad.
60°
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(B) Solving Linear
Trigonometric Equations
One important point to realize  I can
present the same original equation
(sin() = -½ ) in a variety of ways:
(i) 2sin() = -1
(ii) 2sin() + 1 = 0
(iii)  = sin-1(-½)
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(C) Internet Links
Solve Trigonometric Equations from Analyze
Math
Solve Trigonometric Equations - Problems
from Analyze Math
Introductory Exercises from U. of Sask EMR
 try introductory questions first, but skip
those involving proving identities
Solving Trigonometric Equations - on-line
math lesson from MathTV
9
(D) Homework
AW, text page 305, Q1-5
MHR text, p236, Q1-5
Nelson text, p533, Q12
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