cosec18$^\circ$ is a root of the equation :
Solution
$$\cos ec18^\circ = {1 \over {\sin 18^\circ }} = {4 \over {\sqrt 5 - 1}} = \sqrt 5 + 1$$<br><br>Let $\cos ec18^\circ = x = \sqrt 5 + 1$<br><br>$\Rightarrow x - 1 = \sqrt 5$<br><br>Squaring both sides, we get<br><br>${x^2} - 2x + 1 = 5$<br><br>$\Rightarrow {x^2} - 2x - 4 = 0$
About this question
Subject: Mathematics · Chapter: Complex Numbers and Quadratic Equations · Topic: Complex Numbers and Argand Plane
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