If sin theta =4/5& theta is not Frist quadrant ,find the value of cos theta?

1 Answer
Nghi N.
Jun 20, 2018

#cos t = -3/5#

Explanation:

#sin t = 4/5#. Angle t is not in Quadrant 1.
#cos^2 t = 1 - sin^2 t = 1 - 16/25 = 9/25#
#cos t = +- 3/5#
Since t isn't in Quadrant 1, hence, it lies in Quadrant 2, and cos t is negative.
#cos t = -3/5#

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