Question

Find the value of sec18°8'.
(Refer the trigonometric table for the values)

• A. 0.9505
• B. 1.0523
• C. 1.1123
• D. 1.0015

Answer 1

The correct option is B 1.0523

We know that
sec18°8' = $\frac{1}{cos18°8^{\prime }}$ ... (i)
We can write,
18°8' = 18°6' + 2'
From the table we have, cos18°6' = 0.9505
Mean difference for 2′ = 2

cos18°6' = 0.9505
2′ = - 2 (Mean difference to be subtracted for cosine)
____________________
cos18°8' = 0.9503

Put the value of cos18°8' in equation (i)
sec18°8' = $\frac{1}{0.9503}$
sec18°8' = 1.0523