Learning Goal: Students will then be able to use special right triangles to determine geometrically the sine, cosine and tangent for angles that
Agenda:
1. Prior Knowledge Check: Pythagorean Theorem, Definition of Sine, Cosine, and Tangent, Special Right Triangles, Reference Angle and Triangle in degrees or radians.
2. Lesson and Guided Practice: Six Trig Functions, Trig Functions defined in terms of the unit circle
3. Practice Exact Trig Values via the website: http://www.dudefree.com/Student_Tools/materials/precalc/unit-circle.php
4. Organize and Synthesize exact trig values using a table and then using finger tips5. Power Learn using a Mat Activity 6. Homework to reinforce and practice what you have learned.
ฮA
B
C
1.๐น๐๐๐sin ๐ ,cos๐ ,๐๐๐ tan๐6
4
A
B
C A
B
C A
B
C30 ยฐ 45 ยฐ 6 0ยฐ
2. Find all missing sides of the special right triangles.
1 1 1
3. Determine the reference angle and draw the reference triangle:
๐ .150 ยฐ๐ .225 ยฐ๐ . 5๐3 ๐ . โ5๐4
Click Here for Solutions
ฮA
B
C
1.๐น๐๐๐sin ๐ ,cos๐ ,๐๐๐ tan๐6
4
2. Find all missing sides of the special right triangles.
3. Determine the reference angle and draw the reference triangle:
๐ .150 ยฐ๐ .225 ยฐ๐ . 5๐3 ๐ . โ5๐4
20 = 2= a
In Geometry we learned three trigonometric ratios made from the sides of a right triangle. They are sine, cosine, and tangent.
We had an acronym to remember the ratiosโฆโฆSohCahToaโฆโฆ
ฮA
B
C
Hypotenuse
Opp
osite
Adjacent
Next, we will learn three additional trigonometric ratios. They are the reciprocals of sine, cosine, and tangent.
ฮA
B
C
Hypotenuse
Opp
osite
Adjacent
ฮA
B
C
Determine the values of the six trigonometric functions:
53
Using Pythagorean Theorem we determine that AC = 4.
4
Determine the ratios and then
click here.
ฮA
B
C
Determine the values of the six trigonometric functions in quadrant 1 when given:
72
Think of the
solutions then click
here.
Letโs consider our special right triangles and their trigonometric values:
A
B
C A
B
C A
B
C30 ยฐ 45 ยฐ 6 0ยฐ
1 1 1๐๐
โ๐๐
โ๐๐
โ๐๐
๐๐
โ๐๐
If we let the hypotenuse be 1, then sinฮ=y and cosฮ=x . Since the hypotenuse is the radius of a unit circle, we consider it to be radius = r = 1.
Practice the six trig functions for each of the
special angles looking at the triangles above.
You can draw the appropriate triangle, with the reference angle in standard position, having the radius = 1. Next, using your special right triangles skills, you can determine the three basic trig functions: sin, cos, and tan, and then, their reciprocals.
If you know these trig functions, you will be able to determine the values in other quadrants!
Name the six trig functions for each of the three reference triangles above.
Let this be a circle with radius one. Do you see the angles with a 30ยฐ reference angle are indicated with a green dot, angles with a 45ยฐ reference angle are indicated with a red dot, angles with a 60ยฐ reference angle are indicated with a blue dot, and quadrantals are indicated with a pink dot.
Drawing the reference triangle in any of the four quadrants, will give the same numerical answer for the trig functions, however the sign of the trig functions may be different. We can use the saying, โAll Students Take Calculusโ to help remember the signs.
S A
CT
All trig functions are positive in
quadrant 1
Only sin and csc are positive in
quadrant II
Only tan and cot are positive in
quadrant III
Only cos and sec are positive in
quadrant IV
Now, letโs investigate the โquadrantalsโ.
When the terminal side of an angle ฮ that is in standard position lies on one of the coordinate axes, the angle is called a quadrantal angle. The terminal sides of these angles would be located at the pink dots.
Since the coordinates of the pink dots will have 0 and 1, we need to remember the division rules with 0.
http://www.dudefree.com/Student_Tools/materials/precalc/unit-circle.php
Letโs practiceโฆ..When you click the link below, adjust your screen so that you see the circle. Practice the capabilities of the website, by following the directions and doing some trial and error. When finished practicing, deselect the little boxes and choose โquiz meโ. Practice determining sine and cosine, before clicking the flashing circle. Be sure to select other quadrants as well as the first quadrant.
Click the arrow if the website worked.
Click this arrow if the website did NOT work.
http://www.dudefree.com/Student_Tools/materials/precalc/unit-circle.php
These circles can be used if the website does not work. Select a dot for the terminal side, then determine since and cosine of the reference triangle.
Click the arrow to check your answers.
Click the arrow after sufficient practice to continue.
http://www.dudefree.com/Student_Tools/materials/precalc/unit-circle.php
These circles can be used if the website does not work.
Click the arrow to return to the uncovered circle.
Skip practice slide
Letโs consider our special right triangles and their trigonometric values:
A
B
C A
B
C A
B
C30 ยฐ 45 ยฐ 6 0ยฐ
1 1 1๐๐
โ๐๐
โ๐๐
โ๐๐
๐๐
โ๐๐
If we let the hypotenuse be 1, then sinฮ=y and cosฮ=x . Since the hypotenuse is the radius of a unit circle, we consider it to be radius = r = 1.
sinฮ cosฮ tanฮ
30ยฐ โ3
45ยฐ 1
60ยฐ
๐๐
โ๐๐
โ๐๐
๐๐
โ๐๐
โ๐๐
โ๐๐
Now, letโs practice!
Letโs consider our special right triangles and their trigonometric values:
A
B
C A
B
C A
B
C30 ยฐ 45 ยฐ 6 0ยฐ
1 1 1๐๐
โ๐๐
โ๐๐
โ๐๐
๐๐
โ๐๐
If we let the hypotenuse be 1, then sinฮ=y and cosฮ=x . Since the hypotenuse is the radius of a unit circle, we consider it to be radius = r = 1.
sinฮ cosฮ tanฮ
30ยฐ
45ยฐ
60ยฐ
Now, you practiceโฆ Answers
Next Slideor
Your hand can help you rememberโฆ..
Use the following finger tricks!
Hold your hand to remind you of the special angles in the first quadrant.
Think of cosine on top and sine on the bottom. Consider that for the three
specials angles, every answer will be a radical value over two.
Here we go!Fold your angle finger back and
fill-in the radicand with the number of
fingers:top for cosine
and bottom for sine.
sin 30 ยฐ=โ๐2
=12
cos 30ยฐ=
โ๐2
sin 45 ยฐ=โ๐2
cos 45 ยฐ=โ๐2
sin 60 ยฐ=โ๐2
cos 60 ยฐ=โ๐2
The basic trig functions that we have practiced will be used throughout all of PreCalculus and also in Calculus. Therefore, it is important to know them as much as you know your multiplication facts and other computations in mathematics.
Time yourself to complete the โMat Activityโ. Can you complete your โMatโ in under 2 minutes? This knowledge will serve you wellโฆโฆ
The mat is a set of trig functions to be placed in a sheet protector.The solution square are cut-out squares to be placed randomly, face up around the mat. The teacher will use a timer to have students begin and put the appropriate answer square next to its problem. This should be completed in under two minutesโฆ.
or try again!
Play count down PowerPointto time the Mat Activity.
The next slide has the homework. It should be started in class and finished at home.
Upon completion, feel free to check your answers using the website:
http://www.dudefree.com/Student_Tools/materials/precalc/unit-circle.php
Practice: Sketch the reference triangle and determine the exact value of each expression:
1.
2. cos 4 ๐3
3. tan 7๐6
4. cot (โ45 ยฐ )
5. sec (โ90 ยฐ )
6.csc (390 ยฐ )
7. sin 11๐6
8. sin (300 ยฐ )
9.
10. sin (315 ยฐ )
11.cos 11๐312.
13. sec 3๐2
14. sin(โ 5๐3 )15. cos 7๐4
16. cos (โ 19๐6 )17. tan ( 14๐3 )18. csc( 17๐6 )
19.csc๐=2 ,cos๐<0 , h๐ก ๐๐ tan๐=ยฟยฟยฟยฟ
20. sec ๐=โ3๐๐๐๐ก๐๐๐<0 , h๐ก ๐๐ sin๐=ยฟยฟยฟ
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