SMO 2017 Senior Round 1 Question 7
SMO · SMO 2017 Senior Round 1
Suppose $270^\circ\lt \alpha\lt 360^\circ$. Which of the following is equal to $$\sqrt{\cos^3\alpha}-\sqrt{\sin^2\alpha\cos\alpha}\ ?$$
$(\sin\alpha+\cos\alpha)\sqrt{\cos\alpha}$
$(\sin\alpha-\cos\alpha)\sqrt{\cos\alpha}$
$(\cos\alpha-\sin\alpha)\sqrt{\cos\alpha}$
$(-\sin\alpha-\cos\alpha)\sqrt{\cos\alpha}$
$\sqrt{\cos\alpha}$