Let y= array l ( x+ 2 x+ 3 x)^ 2 +( x+ 2 x+ 3 x)^ 2 array then which of the following is…

Mathematics · JEE Advanced · NTA ExamsLimit, Continuity and Differentiability

Let \[y=\sqrt{\begin{array}{l} (\sin x+\sin 2 x+\sin 3 x)^{2} \\ +(\cos x+\cos 2 x+\cos 3 x)^{2} \end{array}}\] then which of the following is correct ?
  1. \(\frac{d y}{d x} \text { when } x=\frac{\pi}{2} \text { is }-2\)
  2. value of y when \(x=\frac{\pi}{5} \text { is } \frac{3+\sqrt{5}}{2}\)
  3. value of y when \(\mathrm{x}=\frac{\pi}{12} \text { is } \frac{\sqrt{1}+\sqrt{2}+\sqrt{3}}{2}\)
  4. y simplifies to (1 + 2 cos x) in [0, π]

Answer

(A) d y d x when x= 2 is -2, (B) value of y when x= 5 is 3+ 5 2

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