How to Find Cos 120 Degrees Value | CBSE Maths Concept Explanation?

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The value of cos 120 degrees

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Cos is one of the trigonometric functions that is defined as the ratio of the adjacent side to the hypotenuse of a right triangle.

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Therefore, to find cos 120o, we need to express 120 in terms of 180⁰ or 90⁰. That is, cos 120 = cos (180−60) or cos 120 = cos (90 + 30).

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We know that, cos (180−x) = −cosx. Therefore, cos (180−60) = −cos 60. Since, cos 60 = ½, cos (180−60) = −cos 60 = −½.

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