E-STAR - Student

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E-Lecture - Cosine of an Angle

In any right triangle the cosine of an angle is the length of the adjacent side divided by the length of the hypotenuse. Cosine is abbreviated by “cos”. In this-sub-topic, we will learn about cosine of an angle and the cosine rule.

Cosine of an angle is used to solve a right triangle. To solve a triangle means to find the lengths of all its sides and the measures of all its angles.

DABC is right triangle. So, the side AC is the side adjacent to angle θ and the side AB is the hypotenuse of right DABC. In solving a right triangle, we use cosine ratio formula:

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E-Lecture - Cosine of an Angle

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