How do you solve? using either factoring, completing the square, or quadratic formula?

Formula - (a-b)(a+b)= a^2 - b^2

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since the cosine is the ratio of the adjacent side to the hypotenuse, you can see that cos 60° = ½. answer. according to the property of cofunctions (topic 3), sin 30° is equal to cos 60°. sin 30° = ½.