Trigonometric Ratios
Applying Background Knowledge of Right Triangles and Ratios
Trigonometric ratios are defined using right triangles
In this lesson, we will first be using our knowledge of right triangles and ratios to geometrically define trigonometric ratios.
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Right triangles have unique characteristics that classify them as right triangles.
Right triangles, like all triangles, have three sides. Each side has a special name. One side is called the hypotenuse. Both of the other two sides are called legs.
Right triangles also have three angles. One of the three angles in a right triangle is a right angle. The other two angles are acute angles.
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A ratio is a comparison between two things relative to each other. For example, if a group of students has 3 girls and 5 boys, then within the group the ratio of girls to boys is 3 to 5. Or, if one student has 21 books and another has 26 books, then the ratio between the amount of books of the first student to the amount of books of the second student is 21 to 26.
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Ratios can be written as fractions comparing one quantity in the numerator to a second quantity in the denominator. The ratio of 3 girls to 5 boys from the previous page can be expressed as seen in the fraction below. 3 is the numerator and 5 is the denominator.
The ratio of 3 girls to 5 boys can be written as a fraction with 3 as the numerator and 5 as the denominator.
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