Given that $y=2 \cos x \sin 2x$, show that \(\frac{ \mathrm{d}y}{ \mathrm{d}x}=k \cos x

Question

Given that $y=2 \cos x \sin 2x$, show that $\frac{ \mathrm{d}y}{ \mathrm{d}x}=k \cos x \cos 2x$, stating the value of k.[4] Hence, show that $\int_0 ^\frac{\pi}{4}(7\cos x \cos 2x+ \sec ^2x) \mathrm{d}x =\frac{7\sqrt 2}{3}+1$[5]

Accepted Answer

(a) $k=3$ (b) $\displaystyle \frac{7\sqrt2}{3}+1$

2025 MSHS PRELIMS P2 Q6

2025 MSHS PRELIMS P2 Q6

Solution:

Solution locked