Question

How do you use a calculator to evaluate $ \sec {79.3^ \circ } $ ?

Answer 1

Hint: To solve this question we should know about trigonometric identity:
Trigonometry: It is the study of the relationship between side length and angle of triangle.
Trigonometry ratio:
A. $ \sin \theta = \dfrac{{prependiucalr}}{{hypotenius}} $
B. $ \cos \theta = \dfrac{{base}}{{hypotenius}} $
C. $ \tan \theta = \dfrac{{prependiucalr}}{{base}} $
D. $ \sec \theta = \dfrac{1}{{\cos \theta }} $
E. $ \cos ec\theta = \dfrac{1}{{\sin \theta }} $

Complete step by step solution:
As we have to calculate $ \sec {79.3^ \circ } $ .
 We know that $ \sec x = \dfrac{1}{{\cos x}} $
So,
  $ \sec {79.3^ \circ } = \dfrac{1}{{\cos {{79.3}^ \circ }}} $
From a calculator, in degree mode:
  $ \dfrac{1}{{\cos {{79.3}^ \circ }}} = \dfrac{1}{{0.1856666154}} $
  $ = 5.385997897 $
We can write it as,
  $ = 5.3860(4dp) $ apporx
If you have a calculator such as Casio $ fx - 83ES $ you can type
  $ \dfrac{1}{{\cos {{79.3}^ \circ }}} $
Directly press = and get the answer immediately without using the reciprocal key.

Note: Trigonometry is used in civil engineering, architecture, measurement of unknown height and many more things.
There are some trigonometry identity:
  $ {\sin ^2}\theta + {\cos ^2}\theta = 1 $
  $ 1 + {\tan ^2}\theta = {\sec ^2}\theta $
  $ 1 + {\cot ^2}\theta = \cos e{c^2}\theta $
There are some other identity:
  $ \tan \theta = \dfrac{{\sin \theta }}{{\cos \theta }} $
  $ \cot \theta = \dfrac{{\cos \theta }}{{\sin \theta }} = \dfrac{1}{{\tan \theta }} $