How do you evaluate $cos^-1 0.8217$ ?

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Answer 1 · 2018-07-15T18:40:53

$\cos^{-1}(0.8217)=34.745^\circ$

One can compute $cos^{-1}(0.8217)$ using calculator

$\cos^{-1}(0.8217)=34.745^\circ$

Answer 2 · 2018-07-15T18:48:54

$34.7° or 325.3°$

The question can be read as ..

"What angle has a cos value of $0.8217$ ?"

If you just need an angle in a right-angled triangle, then on a scientific calculator you would key in:

shift/alt/ $2nd F" "cos^-1 0.8217 =$ to get an angle of $34.7°$

However, if you want to include angles from $0° to 360°$ then we need to consider the sign and decide which quadrants we are working in.

Cos is positive in the first $1st and 4th$ quadrants

The angle in the $1st$ quadrant is $34.7°$ obtained as explained above,

The angle in the $4th$ quadrant is $360-34.7°= 325.3°$

How do you evaluate cos^-1 0.8217cos^-1 0.8217?