How do you evaluate sec( - π / 18) times cos( (37π)/18)?

1 Answer
Nghi N.
May 26, 2016

1

Explanation:

P = sec (-pi/18).cos ((37pi)/18) = (1/cos (-pi/18))cos ((37pi)/18)
cos ((37pi)/18) = cos (pi/18 + 2pi) = cos (pi/18)
Finally, we get:
P = cos (pi/18)/(cos ((-pi)/18))
Since, on the unit circle, cos (pi/18) = cos (-pi/18), therefor
P = 1

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