Find-all-solution-7cos-3x-1-3-for-x-over-the-interval-0-2pi-

Question Number 126005 by bramlexs22 last updated on 16/Dec/20

F i n d a l l s o l u t i o n 7 \cos (3 x) - 1 = 3

f o r x o v e r t h e i n t e r v a l [0, 2 π]

Commented by liberty last updated on 16/Dec/20

7 \cos (3 x) = 4 \Rightarrow \cos (3 x) = \frac{4}{7}

3 x = \cos^{- 1} (\frac{4}{7}) = 0.963

3 x = {\begin{cases} 0.963 + k . 2 π \\ - 0.963 + k . 2 π \end{cases} \Leftrightarrow x = {\begin{cases} 0.321 + \frac{2 k π}{3} \\ - 0.321 + \frac{2 k π}{3} \end{cases}

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