Gujarat BoardEnglish MediumSTD 7MATHSLines and Angles2 Marks
Question
Find an angle which is $2 / 3$ of its complement.
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Answer
Let $x$ be the complement of an angle, then the angle will be $\frac{2}{3} x$. We know that sum of complementary angles is $90^{\circ}$. $ \begin{array}{lc} \text { So, } x+\frac{2}{3} x=90^{\circ} \Rightarrow \frac{3 x+2 x}{3}=90^{\circ} \\ \Rightarrow 5 x=270^{\circ} \\ \Rightarrow x=\frac{270^{\circ}}{5}=54^{\circ} \\ \Rightarrow x=54^{\circ} \\ \therefore \frac{2}{3} \times 54^{\circ}=2 \times 18^{\circ}=36^{\circ} \end{array} $ Hence, complement angle of $54^{\circ}$ is $36^{\circ}$.
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