# How do you calculate  cos A= 0.81?

Jun 7, 2016

See explanation.

#### Explanation:

$\cos A = 0.81$

In this problem, we are asked to find the value of $A$, so that $\cos A$ is equal to $0.81$.

All you need to do is take the inverse of $\cos$ and set it equal to $0.81$.
So:

${\cos}^{-} 1 = 0.81$
${\cos}^{-} 1 \approx 0.63$ (Radians), $35.9$ (Degrees)

So, $A$ can be $0.63 \mathmr{and} 35.9$, depending on which mode you are asked to use.