$\hat{\mathrm{A}} = 2\hat{\mathrm{i}} + 2\hat{\mathrm{j}} - \hat{\mathrm{k}} \mathrm{এবং} \hat{\mathrm{B}} = 6\hat{\mathrm{i}} - 3\hat{\mathrm{j}} + 2\hat{\mathrm{k}} \mathrm{হলে}, \hat{\mathrm{A}} \mathrm{ও} \hat{\mathrm{B}}$ এর অন্তর্ভুক্ত কোণ কত ?

The answer is correct because it represents the angle associated with a specific value calculated from a trigonometric relationship. In this case, the expression given in the answer uses the arccosine function (notated as cos^-1), which helps in finding the angle whose cosine is equal to the given fraction. The fraction in the answer (4/21) corresponds to a specific angle in a right triangle based on the cosine ratio.

To elaborate:

    
• The cosine function relates the angle of a right triangle to the ratio of the length of the adjacent side to the hypotenuse.
    
• When you see cos^-1(4/21), it means you are looking for the angle whose cosine value gives 4/21.
    
• This angle will be given in degrees (or radians) as the output of the arccosine function.

Thus, the answer represents the angle derived from the cosine of that fraction, confirmed by the context of the question.

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