Question

If y = | cos x | + | sin x |, then $\frac{dy}{dx}$ at x = $\frac{2\pi}{3}$ is

• A. $\frac{1 - \sqrt{3}}{2}$
• B. 0
• C. $\frac{1}{2}(\sqrt{3} - 1)$
• D. None of these

Answer 1

Answer: (C)

$\frac{1}{2}(\sqrt{3} - 1)$

Answer 2

y = | cos x | + | sin x |

⇒ at x = 2π/3 = – cos x + sin x

(2^nd quad). dy/dx = sin x + cos x

= sin 2π/3 + cos 2π/3 = $\sqrt{3}$/ 2 – ½