express as a function of a positive acute angle cos 213° is equal to A. cos33° B. -cos33° C. cos57° D. -cos57°?

[匿名]

2017-05-10 1:09 am

回答 (3)

sioieng

2017-05-10 1:19 am

cos(213°)
= cos(180° + 33°) …… cos(213°) is in Quadrant 3, and thus negative.
= -cos(33°)

The answer: B. -cos(33°)

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Jim

2017-05-10 1:16 am

Add or subtract 180

213-180 = 33

So -cos33

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Bryce

2017-05-10 1:12 am

B. -cos33°

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