# How do you calculate arcsin(-0.9871)?

Nov 20, 2015

Find arcsin (-0.9871)

Ans: $- {80}^{\circ} 79 \mathmr{and} - {99}^{\circ} 21$

#### Explanation:

By calculator-->
sin x = -0.9871 --> arc $x = - {80}^{\circ} 79$
Trig unit circle gives another arc $x = - {99}^{\circ} 21$ that has the same sine value.
If you want the answers by the opposite direction of rotation, then the 2 answers are:
x = 180 + 80.79 = ${260}^{\circ} 79$ and
x = 180 + 99.21 = ${279}^{\circ} 21$

Check by calculator
sin (260.79) = -0.9871. OK
sin (279.21) = - 0.9871. OK