Question

Using trigonometric tables, find the approximate value of cos 54° 26'.

Answer 1

Given: cos 54° 26'

Step-wise calculation:

1. Use the identity cos θ = sin (90° – θ).

So, cos 54° 26' = sin (90° – 54° 26')

= sin 35° 34'

2. Read the value of sin 35° 34' from trigonometric tables. 

From the tables,

sin 35° 34' ≈ 0.5816.

cos 54° 26' ≈ 0.5816.