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

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Answer 1 · 2018-02-27T00:47:06

#color(red)(A=216.87^@)#

.

#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.