Chapter 8: Properties of Special Right Triangles & Trigonometry
Resources
Chapter Reviews
Thanks to Ishwari, Jaansi & Lekhana
8.1 - Geometric Mean
Thanks to Ishwari Veerkar & Riya Chowdawarapu
Answer Key Worksheet #1 - Riya C
8.2 - Pythagorean Theorem & it's Converse
Thanks to Ishwari Veerkar
Kuta Worksheet #2 (Advanced)
Worksheet #3 - (Highly Recommended)
8.3 - Special Right Triangles
Thanks to Ishwari Veerkar, Riya Chowdawarapu
Kuta Worksheet #2 - (Highly Recommended)
Answer Key WS #2 - Riya C
Word Problem Practice with Answers
8.4 - Trigonometry
Thanks to Ishwari Veerkar
Kuta Worksheet #4 - Recommended
Worksheet #6 - Recommended
8.5 - Angles of Elevation and Depression
Thanks to Ishwari Veerkar
Worksheet #2 - No Answer Key
8.6 - Law of Sines and Cosines
Thanks to Ishwari Veerkar and Nidhi
Law of Sines and Cosines Practice
Word Problem Worksheet -HIGHLY RECOMMENDED
Notes
8.1 - Geometric Mean
Thanks to GMChonk (Rachit Surve)
Geometric mean is when you have two ratios, compared in the form a/b = b/x.
After cross multiplication, b^2 = ax, so b = sqrt ax. For example, the geometric mean of 5 and 45 is 15, because
5/x = x/45 - plug numbers into formula
5 * 45 = x*x - cross multiply
x^2 = 225
sqrt (x^2) = sqrt 225 - isolate x by taking sqrt of both sides
x = 15. In this scenario, a and x are means and b is an extreme.
The shortcut is to plug the numbers into the formula b = sqrt ax; b = sqrt 45 * 5; b = 15
Steps done by: Nikola Birac
8.2 - Pythagorean Theorem & Its Converse
Thanks to GMChonk (Rachit Surve)
Pythagorean Theorem is used to find if triangles are right triangles. If the sides of a triangle a, b, and c are such that a^2 + b^2 = c^2, then the triangle is a right triangle. If a^2 + b^2 > c^2, then the triangle is acute. If a^2 + b^2 < c^2, then the triangle is obtuse.
Some common Pythagorean sets you should know are 3 - 4 - 5, 5 - 12 - 13, 8 - 15 - 17, and 7 - 24 - 25. Any triangles with these sides, or all sides in proportion to these measures, are right triangles.
8.3 - Special Right Triangles
Thanks to GMChonk (Rachit Surve)
45 - 45 - 90 triangles have side lengths such that the legs are x and the hypotenuse is x times sqrt 2. To get a leg from the hypotenuse, divide by sqrt 2, and to get a hypotenuse from a leg, multiply by sqrt 2.
30 - 60 - 90 triangles have side lengths such that the shortest leg(opposite the 30 degree angle) is x, the longer leg (opposite the 60 degree angle) is x times sqrt 3, and the hypotenuse (opposite the right angle) is 2x.
8.4 - Trigonometry
Thanks to Ishwari Veerkar and Thomas Catuosco
SOH CAH TOA
Sine --> Opposite/ Hypotenuse
Cosine --> Adjacent/ Hypotenuse
Tangent --> Opposite/ Adjacent
On a calculator, they are spelled out as sin, cos, tan. MAKE SURE TO HAVE YOUR CALCULATOR IN DEGREE FORM!!!
The inverse is written as sin^-1, cos^-1, and tan^-1. They are also known as arcsine, arccosine, and arctangent. -------- - Nikola Birac
8.5 - Angles of Elevation & Depression
Thanks to Ishwari Veerkar
An Angle of Elevation is the angle formed by a horizontal line and an observer's line of sight to an object above the horizontal line.
An Angle of Depression is formed by a horizontal line and an observer's line of sight to an object below the horizontal line.
8.6 - Law of Sines and Cosines
Thanks to Ishwari Veerkar & Nishi Agrawal
Law of Sines: If the 3 sides namely a, b, c are opposite to the respective angles measuring A, B, C then
sin A/a = sin B/b = sin C/c
Law of Cosines: If the 3 sides namely a, b, c are opposite to the respective angles measuring A, B, C then
*can be used if you have SSS and need to find an angle or if you have SAS and are trying to find another side*
Essentially, if you have less than 2 angle measures, use this law.
a^2 = b^2 + c^2 - 2bc(cos A)
b^2 = a^2 + c^2 - 2ac(cos B)
c^2 = a^2 + b^2 -2ab(cos C)
Note: Uppercase letter variables mean angle measures while lowercase letter variables mean side lengths. And always remember that if you are trying to find an angle measure if you are given side lengths of any triangle, use the inverse trigonometric ratios (sin^-1, cos^-1, tan^-1). - Nikola Birac