Verified Answer :

AL2006

If tan(x)·cos(x) = cos(x),

then tan(x) = cos(x) / cos(x) = 1

The angles whose tangent is ' 1 ' are 45° and 225° .

\(0 \leq x\leq2\pi\ and\ x eq\frac{\pi}{2}\ and\ x eq\frac{3\pi}{2}\\\\tanx\cdot cosx=cosx\\\\tanx\cdot cosx-cosx=0\\\\cosx(tanx-1)=0\iff cosx=0\ \vee\ tanx=1\\\\x=\frac{\pi}{2} otin D\ \vee\ x=\frac{3\pi}{2} otin D\ \vee\ x=\frac{\pi}{4}\in D\ \vee\ x=\frac{5\pi}{4}\in D\)

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