Integrate__
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Answers
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➠ ᴍᴜʟᴛɪᴘʟʏɪɴɢ ʙᴏᴛʜ ɴᴜᴍ. ᴀɴᴅ ᴅᴇɴ. ʙʏ 2 ᴡᴇ ɢᴇᴛ,
➠ ʟᴇᴛ ɪɴ ɪ1
➻
➠ ʟᴇᴛ ɪɴ ɪ2
➻
➠ ᴏɴ sᴜʙsᴛɪᴛᴜᴛɪɴɢ, .
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⋘ ─────── ∗ ⋅◈⋅ ∗ ─────── ⋙
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$$\begin{lgathered}\blue{\implies} \int\limits \frac{1}{ \sin(x) + \sec(x) } dx \\ \\ \blue{\implies} \int\limits \frac{1}{ \sin(x) + \frac{1}{ \cos(x) } } dx \\ \\ \blue{\implies} \int\limits \frac{ \cos(x) }{1 + \sin(x) \cos(x) } dx\end{lgathered}$$
ᴍᴜʟᴛɪᴘʟʏɪɴɢ ʙᴏᴛʜ ɴᴜᴍ. ᴀɴᴅ ᴅᴇɴ. ʙʏ 2 ᴡᴇ ɢᴇᴛ,
$$\begin{lgathered}\blue{\implies} \int\limits \frac{2 \cos(x) }{2 \sin(x) \cos(x) + 2} \\ \\ \blue{\implies} \int\limits \frac{( \cos(x) - \sin(x) ) + ( \cos(x) + \sin(x) ) }{1 + 1 + 2 \sin(x) \cos(x) } dx \: \: \: \: \: \: \: \: \: \: \: \: \: \: \red{{ \sin(x) }^{2} + { \cos(x) }^{2} = 1 } \\ \\ \blue{\implies} \int\limits \frac{( \cos(x) - \sin(x)) + ( \cos(x) + \sin(x) ) }{1 + {( \sin(x) + \cos(x) ) }^{2} } \\ \\ \blue{\implies} \int\limits \frac{( \cos(x) - \sin(x)) }{1 + {( \sin(x) + \cos(x)) }^{2} } dx + \int\limits \frac{( \cos(x) + \sin(x)) }{1 + {( \sin(x) + \cos(x) )}^{2} } dx \\ \\ \blue{\implies} \int\limits \frac{( \cos(x) - \sin(x)) }{1 + {( \sin(x) + \cos(x) }^{2} } dx + \int\limits \frac{( \cos(x) + \sin(x) )}{1 + {2 - ( { \sin(x) - \cos(x)) }^{2}} } dx \\ \\ \blue{\implies} \int\limits \underbrace{\bf\purple{{\bigg[ \frac{( \cos(x) - \sin(x) )}{1 + {( \sin(x) + \cos(x) )}^{2} } \bigg]}}}dx + \int\limits \underbrace{\bf\purple{{\bigg[ \frac{( \cos(x) + \sin(x)) }{3 - ( {\sin(x) - \cos(x)}^{2} ) } \bigg]}}}dx \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: I_1 \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: I_2\end{lgathered}$$
➨ ʟᴇᴛ ɪɴ ɪ1
❧ $$\begin{lgathered}\sin(x) + \cos(x) = t \\ {\cos(x) - \sin(x) }dx = dt\end{lgathered}$$
➨ʟᴇᴛ ɪɴ ɪ2
❧ $$\begin{lgathered}\sin(x) - \cos(x) = v \\ { \cos(x) + \sin(x) }dx = dv\end{lgathered}$$[/tex]
➨ ᴏɴ sᴜʙsᴛɪᴛᴜᴛɪɴɢ, .
$$\begin{lgathered}\blue{\implies} \int\limits \frac{dt}{1 + {t}^{2} } + \int\limits \frac{dv}{3 - {v}^{2} } \\ \\ \blue{\implies} { \tan }^{-1} t \: + \frac{1}{2 \sqrt{3} } log \bigg| \frac{ \sqrt{3} - v }{ \sqrt{3} + v} \bigg| + C \\ \\ \blue{\implies} \purple{ { \tan}^{-1}( \sin(x) + \cos(x) ) } \purple{+ \frac{1}{2 \sqrt{3} }} \purple{ log \bigg| \frac{ \sqrt{3} - \sin(x) + \cos(x) }{ \sqrt{3} + \sin(x) - \cos(x) } \bigg| + C}\end{lgathered}$$
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