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Geometry Notes
Lesson 5.3A – Trigonometry
T.2.G.6 Use trigonometric ratios (sine, cosine, tangent) to
determine lengths of sides and measures of angles in right
triangles including angles of elevation and angles of
depression
T.2.G.7 Use similarity of right triangles to express the sine,
cosine, and tangent of an angle in a right triangle as a ratio
of given lengths of sides
Vocabulary
• Trigonometry – Triangle Measurement
Trigonometric Ratios
opposite
sine =
hypotenuse
A
c
b
C
a
adjacent
cosine =
hypotenuse
B
opposite
tangent =
adjacent
A
c
b
C
sin A =
cos A =
tan A =
a
B
sin B =
cos B =
tan B =
Example 1
• Find the sine, cosine, and tangent of A
and B.
A
5
4
C
3
B
sin A =
sin B =
cos A =
cos B =
tan A =
tan B =
Writing Trig Ratios
Pythagorean Theorem , find the missing side.
1. Using the ___________________
2. Label each side according to the angle θ.
3. Write the ratio for sine, cosine, and tangent.
θ
6
4