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# trigonometry write the expression as a single real number. do not use decimal appox.?

cos(2π/3)cosπ + sin(2π/3)sinπ

can you show me how and if anyone tell me all the common angles

and a good complete unit circle with the degree, radian and the coordinates

### 3 Answers

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- PopeLv 71 decade ago
cos(2π/3) = -1/2

cos(π) = -1

sin(2π/3) = √(3)/2

sin(π) = 0

So far as the tables and diagrams you requested, they might be found in a secondary textbook appendix. A good study strategy is to become familiar with the ratios in the 45°–45°–90° and 30°–60°–90° triangles, and learn the signs of the trigonometric functions in the four quadrants. The key is to understand rather than memorize.

- 1 decade ago
we can simplify the problem by finding the numerical values of the given functions.

cos(2pi/3) = -.5

cos(pi) = -1

sin(2pi/3) = squareroot(3) / 2

sin(pi) = 0

so,

-.5(-1) + 0 = 1.5

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