Introduction to Trigonometry

Intro to Trig Ratios

​Labeling Sides

​When using trigonometric ratios, labeling the sides correctly is VERY IMPORTANT.

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​If you label the sides incorrectly, you will end up with the wrong answer.

​Reference Angle

When completing trig problems, you will always know at least 2 angles- the 90° angle and the reference angle.

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​You will identify your sides based on the reference angle.

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​Sometimes this angle is called Θ (theta).

Label your sides

Opposite- the side across from your reference angle. ​

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​Adjacent- the side between the reference angle and the right angle

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​Hypotenuse- the longest side, it's across from the right angle.

New Trig Ratios

• Cosecant (csc) : reciprocal of Sine

• Secant (sec): reciprocal of cosine

• Cotangent (cot): reciprocal of tangent

Multiple Choice

What is the side adjacent of C?

• 7

• 24

• 25

Multiple Choice

What is sinC = ?

• 24/25

• 7/25

• 24/7

Multiple Choice

What is cosC = ?

• 24/25

• 7/25

• 24/7

Multiple Choice

What is tanC = ?

• 24/25

• 7/25

• 24/7

• 7/24

Multiple Choice

What is the hypotenuse?

• 6

• 8

• 10

Multiple Choice

What is the side opposite of A?

• 6

• 8

• 10

Multiple Choice

What is the side adjacent to A?

• 6

• 8

• 10

Multiple Choice

What is the sinA = ?

• 6/10 = 3/5

• 8/10 = 4/5

• 6/8 = 3/4

• 8/6 = 4/3

Multiple Choice

What is the cosA = ?

• 6/10 = 3/5

• 8/10 = 4/5

• 6/8 = 3/4

• 8/6 = 4/3

Multiple Choice

What is the tanA = ?

• 6/10 = 3/5

• 8/10 = 4/5

• 6/8 = 3/4

• 8/6 = 4/3