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Mathematics 24 Online
OpenStudy (anonymous):

Find the exact value of the cosine of 75 degrees. Since we can write 75 degrees as the sum of 45 and 30 degrees, we can write cos(75°) = cos(45° + 30°) = cos45°cos30° - sin45°sin30° ... Can someone explain how to get 45 and 30

OpenStudy (anonymous):

because 45 + 30 = 75 ?

OpenStudy (anonymous):

You need to use the rules of special triangles 30-30-60 and 45-45-90. Do you know those?

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