Answer with explanation:
We will use Cosine law to find value of Side, RT whose length =s.
Cosine Law in Mathematical terms, that is , if a, b and c are sides of triangle
\(b^2=c^2 +a^2-2 a c \cos B\\\\ \text{ In} \Delta RST\\\\s^2=9^2+8^2-2\times 9 \times 8 \times \cos111^{\circ} \\\\s^2=81 +64 -144 \times (-\cos 69^{\circ})\\\\\cos111^{\circ}=cos (180-69^{\circ})\\\\=-\cos 69^{\circ}\\\\s^2=81 +64 -144 \times(- 0.358)\\\\s^2=145+51.55\\\\s^2=196.552\\\\s=14.0197\)
→Cosine is negative in second quadrant, so value of cosine 111 is negative.
⇒Rt=s=14.0
⇒Option D : 14
