Question5. Eliminate $\theta$ from each of the following pairs of expressions. (a) $x+1=\cos 2 \theta, y=\sin \theta$, (c) $y-3=\cos 2 \theta, x=2-\sin \theta$.
6. Angle $D$ is acute and $\tan D=\frac{3}{4}$. Find (a) $\sin D$, (b) $\sin 2 D$, (c) $\sin \left(\frac{1}{2} D\right)$.
7. Angle $E$ lies between $0^{\circ}$ and $360^{\circ}$. Find $\sin \left(\frac{1}{2} E\right)$ given that $\cos E$ is (a) $\frac{3}{8}$, (b) $-\frac{3}{8}$.
8. (a) Obtain an expression for $\sin 3 \theta$ involving powers of $\sin \theta$. (b) If $\sin \theta=\frac{1}{4}$ find the value of $\sin 3 \theta$.
9. (a) Obtain an expression for $\cos 3 \theta$ involving power of $\cos \theta$. (b) If $\sin \theta=1 / \sqrt{ } 5$ and $\theta$ is obtuse, find the value of $\cos 3 \theta$.
10. In triangle $\mathrm{ABC}, \mathrm{BÂC}=$