Đáp án + Giải thích các bước giải:
`h.`
`cos2x-5sinx-3=0`
`<=>1-2sin^2x-5sinx-3=0`
`<=>-2sin^2x-5sinx-2=0`
`<=>2sin^2x+5sinx+2=0`
`<=>`\(\left[ \begin{array}{l}\sin x=-\dfrac{1}{2}\\\sin x=-2(VN)\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=-\dfrac{\pi}{6}+k2\pi\\x=\dfrac{7\pi}{6}+k2\pi\end{array} \right.\)`(kinZZ)`
`i.`
`5tanx-2cotx-3=0`
ĐKXĐ: `xne(kpi)/2`
`PT<=>5tanx-2. 1/tanx-3=0`
`<=>5tan^2x-3tanx-2=0`
`<=>`\(\left[ \begin{array}{l}\tan x=1\\\tan x=-\dfrac{2}{5}\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=\dfrac{\pi}{4}+k\pi\\x=\arctan(-\dfrac{2}{5})+k\pi\end{array} \right.\)`(kinZZ)`
