Question

Find the value of cos(2580°)

Answer 1

$\underline{\textbf{Given:}}$

$\mathsf{cos(2580^\circ)}$

$\underline{\textbf{To find:}}$

$\mathsf{The\;value\;of\;cos(2580^\circ)}$

$\underline{\textbf{Solution:}}$

$\mathsf{Consider,}$

$\mathsf{cos(2580^\circ)}$

$\mathsf{=cos(2520^\circ+60^\circ)}$

$\mathsf{=cos(7{\times}360^\circ+60^\circ)}$

$\mathsf{=cos\,60^\circ}$

$\mathsf{=\dfrac{1}{2}}$

$\implies\boxed{\bf\,cos(2580^\circ)=\dfrac{1}{2}}$

$\underline{\textbf{Coterminal angles:}}$

$\boxed{\begin{minipage}{8cm} \\\textsf{Angles have same initial side and terminal side}\\\\\textsf{but with different amount of rotations are}\\\\\textsf{called Coterminal angles}\\\\\mathsf{Here,\;2580^\circ\;and\;60^\circ\;are\;coterminal\;angles}\\ \end{minipage}}$