How do you find the exact Trigonometric value in simplest form given secA = -5/4 and 180º < A < 270º, Find sin 2A ?

1 Answer
Feb 27, 2018

color(red)(A=216.87^@)

Explanation:

.

180^@ < A < 270^@

secA=-5/4

1/cosA=-5/4

cosA=-4/5

A=arccos(-4/5)=143.13^@, 216.87^@

Of the two possibilities, only the second one falls in the specified range.