MCQ
${ }^{47} C _4+\sum_{r=1}^5{ }^{52-r} C _3$ is equal to :
- A${ }^{51} C _4$
- ✓${ }^{52} C _4$
- C${ }^{53} C _4$
- DNone of these
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The real value of $\theta$ for which the expression $\frac{1+\text{i}\cos\theta}{1-2\text{i}\cos\theta}$ is a real number is:
$\text{n}\pi+\frac{\pi}{4}$
$\text{n}\pi+(-1)^{\text{n}}\frac{\pi}{4}$
$2\text{n}\pi\pm\frac{\pi}{2}$
None of these.
The set $(\text{A} \cap \text{B}')' \cup (\text{B} \cap \text{C})$ is equal to.
$\text{A}'\cup\text{B}\cup\text{C}$
$\text{A}'\cup\text{B}$
$\text{A}'\cup\text{C}'$
$\text{A}'\cap\text{B}$