Use a reference triangle in an appropriate quadrant to find the angle.
-$\cos ^ { - 1 } \left( \frac { 1 } { \sqrt { 2 } } \right)$
A) $\frac { 4 } { \pi }$
B) $\frac { \pi } { 2 }$
C) $\frac { 2 \pi } { 3 }$
D) $\frac { 3 \pi } { 4 }$

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The Answer of Use a reference triangle in an appropriate quadrant to find the angle.
-$\cos ^ { - 1 } \left( \frac { 1 } { \sqrt { 2 } } \right)$
A) $\frac { 4 } { \pi }$
B) $\frac { \pi } { 2 }$
C) $\frac { 2 \pi } { 3 }$
D) $\frac { 3 \pi } { 4 }$

Use a Reference Triangle in an Appropriate Quadrant to Find cos⁡−1(12)\cos ^ { - 1 } \left( \frac { 1 } { \sqrt { 2 } } \right)cos−1(2​1​)

Use a Reference Triangle in an Appropriate Quadrant to Find $\cos ^ { - 1 } \left( \frac { 1 } { \sqrt { 2 } } \right)$