AAT 5 - Math is Fun with Erxleben



Right Triangle Trig Review Notes

Trigonometry – means “triangle measure”

hypotenuse – the longest side of a right triangle; the side opposite (across) from the right angle

legs – the shorter two sides opposite the acute angles

adjacent – means to be next to or touching

opposite – means to be across from

Name Symbol Definition

|Trigonometric Ratios |sine θ |sin θ |opposite side | |

| | | |hypotenuse | |

| |cosine θ |cos θ |adjacent side | |

| | | |hypotenuse | |

| |tangent θ |tan θ |opposite side | |

| | | |adjacent side | |

The hypotenuse is always the same regardless which acute angle you label as θ. The adjacent and opposite sides will switch depending which acute angle you label as θ.

SOH – CAH – TOA: mnemonics device for remembering right triangle trig ratios

SOH – CAH - TOA

|Sine is Opposite over Hypotenuse |Cosine is Adjacent over Hypotenuse |Tangent is Opposite over Adjacent |

SOH CAH TOA Story

A young Indian, frustrated by his inability to understand the geometric constructions of his tribe's battle dress, kicked out in anger against a stone and crushed his big toe. Fortunately, he learned from this experience, and began to use study and concentration to solve his problems rather than violence and injure himself. This was especially effective in his study of math, and he went on to become the wisest man of his tribe. He studied many aspects of trigonometry; and even today we remember many of the functions by his name. When he became an adult, the tribal priest gave him a name that reflected his special nature -- one that reminded them of his great discoveries and of the event which changed his life. Because he was troubled throughout his life by the problematic toe that he injured by kicking the stone, he was constantly at the edge of the river, soaking his toe in the cooling waters. For that behavior, he was named Chief Soh Cah Toa.

Examples: 1. Find the values for all 3 trig functions for angle A and angle B.

|sin(A) = |sin(B) = |

|cos(A) = |cos(B) = |

|tan(A) = |tan(B) = |

2. Find the three trig values for angle E.

|sin(E) = |

|cos(E) = |

|tan(E) = |

If irrational numbers are encountered (numbers with radicals like[pic]), they should be reduced and rationalized.

45°-45°-90° and 30°-60°-90° Right Triangles

Recall these special right triangles.

Fill in the following chart using trig ratios. These are common angles, so you should have these values memorized (concentrate on sine, cosine, and tangent).

|θ |sin θ |cos θ |tan θ |

|30° | | | |

|45° | | | |

|60° | | | |

Look at the values that are the same in this chart. Do you notice a pattern?

-----------------------

c

C

Pythagorean Theorem

a2 + b2 = c2

B

a

b

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legs

Angles are labeled with capital letters (A, B, C) while the sides opposite them are labeled with the corresponding lower case letters (a, b, c).

A

hypotenuse

θ

adjacent

opposite

B

8 cm

15cm

C

A

7 in

E

F

3 in

D

60°

|sin(A) = |

|cos(A) = |

|tan(A) = |

|csc(A) = |

|sec(A) = |

|cot(A) = |

45°

x[pic][pic]

x

x

x[pic][pic]

x

2x

30°

45°

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