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Lessons 1 5.notebook February 05, 2015
Find the Missing Angle of a Right Triangle
(using Trig)
Intermediate Algebra HVCC
Quarter 3
Trigonometry
Objectives:
• Students can examine a right triangle and determine relationships based on trigonometry.
Lessons 1 5.notebook February 05, 2015
Gettin' Triggy Wit It?
Pay special attention to the part where they are looking for an angle!
http://www.youtube.com/watch?v=t2uPYYLH4Zo
So now we know there are two ways to find the missing side of a right triangle:
1. Pythagorean Theorem (if we have 2 sides and are looking for the third side).
2. Trigonometry (if we know one angle and the length of one side).
But how can we find the missing angle of a right triangle if we know the measure of two if the sides?
I can find the missing angle using Trig
Lessons 1 5.notebook February 05, 2015
Look at your calculator. You will notice above the "sin," "cos," and "tan" keys there are the following:
We will use these keys today to find the measure of a missing angle in a right triangle.
I can use the correct buttons to use to find angle
Inverse Operations for Trigonometry(used to find the angle in a right triangle)
Trig Function: Inverse Trig Function:How you say it:sin (x)sin1 (x) Inverse sin of xarcsin (x)
cos (x)cos1 (x) Inverse cos of x
arccos (x)
tan (x) tan1 (x) Inverse tan of x
arctan (x)
I can read Trig inverse buttons correctly
Lessons 1 5.notebook February 05, 2015
x
40
50
Look at the right triangle shown. Set up a trigonometric equation that you
could use to find x to the nearest tenth.
I can find the missing angle using Trig
x
40
50
Since you are looking for the angle, we must use do the opposite or INVERSE of "cos". The "cos1" will be used to find our angle.
I can find the missing angle using Trig
Lessons 1 5.notebook February 05, 2015
x
15
10
Try this example and find x to the nearest degree.
So the moral of the story is that when you are looking for an angle, you MUST use the INVERSE operation!!!
I can find the missing angle using Trig
x
257
Try these examples and find x to the nearest tenth.
x11
31. 2.
I can find the missing angle using Trig
Lessons 1 5.notebook February 05, 2015
x
11 3
Try these examples and find x to the nearest degree.
x517
2.1.
I can find the missing angle using Trig
A light post is set in concrete and supported by a wire while the concrete
dries. The length of the wire is 10 feet and the ground stake is 4 feet from the bottom of the light post. Find the measure of the angle that the wire makes with the ground
to the nearest degree.
x
I can find the missing angle using Trig
Lessons 1 5.notebook February 05, 2015
Homework:p. 4 #1 14
Homework