# How do you calculate cos^-1 (2.3/5.4)?

Jun 4, 2016

64.8°

#### Explanation:

The question is asking " What angle in a right-angled triangle has the ratio of the adjacent side to the hypotenuse as $\frac{2.3}{5.4}$?

First find the ratio in decimal form by dividing.
2.3÷5.4 = 0.4259259

This is the value of the Cos of our known angle. To find the angle you either need to use a calculator or a table.

Cos x = 0.4259259 rArr x = 64.8°

Do the calculation on a calculator, then press 2nd function/shift and Cos.
Some calculators need the = sign pressed, others will give tha answer immediately.

You can also key it in as:
shift cos (2.3÷5.4) =