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

1 Answer
Jun 4, 2016



The question is asking " What angle in a right-angled triangle has the ratio of the adjacent side to the hypotenuse as #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) =