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8. Introduction to Trigonometry
easy
$2 \sin ^{2} 30 \cot 30-3 \cos ^{2} 60 \sec ^{2} 30=\ldots \ldots \ldots$
A
$\frac{\sqrt{3}-1}{2}$
B
$\frac{\sqrt{3}-2}{2}$
C
$0$
D
$1$
Solution
$2 \sin ^{2} 30 \cot 30-3 \cos ^{2} 60 \sec ^{2} 30=2\left(\frac{1}{2}\right)^{2} \sqrt{3}-3\left(\frac{1}{2}\right)^{2}\left(\frac{2}{\sqrt{3}}\right)^{2}$
$=2 \times \frac{1}{4} \times \sqrt{3}-3 \times \frac{1}{4} \times \frac{4}{3}$
$=\frac{\sqrt{3}}{2}-1=\frac{\sqrt{3}-2}{2}$
Standard 10
Mathematics