Video: Calculating the Cosine Function of a Given Angle

Use a calculator to find cos of 56.3° to four decimal places.

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Video Transcript

Use a calculator to find cos of 56.3 degrees to four decimal places.

Typing cos 56.3 into the calculator gives us 0.5548444274. In this question, we’re asked to round our answer to four decimal places. Therefore, we need four numbers after the decimal point. As the four after the dotted line is less than five, we’re going to round down. This gives us 0.5548 to four decimal places.

We know that cos of 45 is root two divided by two and cos of 60 is one-half. Root two divided by two is equal to 0.7071 and a half is the same as 0.5. As 56.3 degrees is between 45 and 60 degrees, then our answer needs to be between these two values. As 0.5548 is greater than 0.5, but less than 0.7071, our answer is sensible.

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