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Intro to . Part 1
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What is Trigonometry?
• Trig. is the branch of mathematics that studies the ratios between the sides and angles of triangles which can then be used in many other areas of math.
• These ratios are:
– Sine, pronounced “sign”
– Cosine, pronounced “co-sign”
– Tangent
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Why Trig?
• If you want to find missing sides or angles in a right triangle BUT:
– You can’t use Pythag. Theorem bc you don’t have 2 of the 3 sides.
– You can’t use 45-45-90 tricks bc you don’t have THOSE angles.
– You can’t use 30-60-90 tricks bc you don’t have THOSE angles.
• THEN YOU USE TRIG!!!
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Some basic terms:
Opposite: The side directly across from the reference angle.
Hypotenuse: The side directly across from the right angle. Adjacent: The leg next
to the reference angle that is NOT the hypotenuse. (Use process of elimination to find this side last.)
Reference Angle: ONE of the 2 ACUTE angles in the right triangle. From this angle you will name the 3 sides like below.
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Some basic terms:
Opposite: The side directly across from the reference angle.
Hypotenuse: The side directly across from the right angle.
Adjacent: The leg next to the reference angle that is NOT the hypotenuse. (Use process of elimination to find this side last.)
Reference Angle
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So how do we find those missing sides/angles?
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If you like steps
1. Pick an ACUTE reference angle.
2. Label sides Opp, Adj, & Hyp based on #1.
3. Ask these questions to decide which part of SohCahToa to use:
1. What was I given?
2. What am I finding?
4. Set up equation using SohCahToa
5. Solve using algebra.
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Solve each right Triangle.
1.)
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3.)