উত্তর সিলেক্ট করলে সঠিক ও ভুল দেখাবে।
ব্যাখ্যা ও সঠিক সমাধান
উত্তর:
2 cos x2
cot((x1+x2)/2) cot((x1-x2)/2) = 3 => cos((x1+x2)/2)cos((x1-x2)/2) / sin((x1+x2)/2)sin((x1-x2)/2) = 3/1. Applying componendo and dividendo: (cos((x1+x2)/2)cos((x1-x2)/2) + sin((x1+x2)/2)sin((x1-x2)/2)) / (cos((x1+x2)/2)cos((x1-x2)/2) - sin((x1+x2)/2)sin((x1-x2)/2)) = (3+1)/(3-1) => cos((x1+x2)/2 - (x1-x2)/2) / cos((x1+x2)/2 + (x1-x2)/2) = 4/2 => cos x2 / cos x1 = 2 => cos x1 = cos x2 / 2. Note: The provided options seem to imply a different arrangement or typo in the question/options, but based on the derivation, cos x1 = 1/2 cos x2.