Question : The value of the expression $\sin^{2}1^{\circ}+\sin^{2}11^{\circ}+\sin^{2}21^{\circ}+\sin^{2}31^{\circ}+\sin^{2}41^{\circ}+\sin^{2}45^{\circ}+\sin^{2}49^{\circ}+\sin^{2}59^{\circ}+\sin^{2}69^{\circ}+\sin^{2}79^{\circ}+\sin^{2}89^{\circ}$ is:
Option 1: $0$
Option 2: $5\frac{1}{2}$
Option 3: $5$
Option 4: $4\frac{1}{2}$
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Correct Answer: $5\frac{1}{2}$
Solution : $\sin^{2}1^{\circ}+\sin^{2}11^{\circ}+\sin^{2}21^{\circ}+\sin^{2}31^{\circ}+\sin^{2}41^{\circ}+\sin^{2}45^{\circ}+\sin^{2}49^{\circ}+\sin^{2}59^{\circ}+\sin^{2}69^{\circ}+\sin^{2}79^{\circ}+\sin^{2}89^{\circ}$ Using the identity $\sin(90^{\circ} - \theta) = \cos\theta$, we get, $\sin^{2}49^{\circ}=\sin^{2}(90^\circ-41^{\circ}) = \cos^2{41}^\circ$ $\sin^{2}59^{\circ}=\sin^{2}(90^\circ-31^{\circ}) = \cos^2{31}^\circ$ $\sin^{2}69^{\circ}=\sin^{2}(90^\circ-21^{\circ}) = \cos^2{21}^\circ$ $\sin^{2}79^{\circ}=\sin^{2}(90^\circ-11^{\circ}) = \cos^2{11}^\circ$ $\sin^{2}89^{\circ}=\sin^{2}(90^\circ-1^{\circ}) = \cos^2{1}^\circ$ $=\sin^{2}1^{\circ}+\sin^{2}11^{\circ}+\sin^{2}21^{\circ}+\sin^{2}31^{\circ}+\sin^{2}41^{\circ}+\sin^{2}45^{\circ}+\cos^{2}41^{\circ}+\cos^{2}31^{\circ}+\cos^{2}21^{\circ}+\cos^{2}11^{\circ}+\cos^{2}1^{\circ}$Each pair adds up to $1$ because $\sin^{2}\theta + \cos^{2}\theta = 1$ $=5+\sin^{2}45^{\circ}$ $=5+\frac{1}{2}$ $=\frac{11}{2}=5\frac{1}{2}$ Hence, the correct answer is $5\frac{1}{2}$.
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Question : The value of $\frac{\operatorname{sin} 58^{\circ}}{\cos 32^{\circ}}+\frac{\sin 55^{\circ} \sec 35^{\circ}}{\tan 5^{\circ} \tan 45^{\circ} \tan 85^{\circ}}$ is equal to:
Option 1: 2
Option 2: 1
Option 3: 0
Option 4: 3
Question : The value of ($\sin 45^\circ+\cos 45^\circ$) is___________.
Option 1: $\frac{2}{\sqrt{2}}$
Option 2: $\frac{1}{\sqrt{2}}$
Option 3: $1$
Option 4: ${\sqrt{2}}$
Question : If $\sin (\theta +18^{\circ})=\cos 60^{\circ}(0< \theta < 90^{\circ})$, then the value of $\cos 5\theta$ is:
Option 1: $\frac{1}{2}$
Option 2: $0$
Option 3: $\frac{1}{\sqrt{2}}$
Option 4: $1$
Question : Find the value of $\frac{\cos^{2}25^\circ-\sin^{2}65^\circ}{\cos^{2}25^\circ+\sin^{2}65^\circ}$
Option 2: $1$
Option 3: $–1$
Option 4: $0$
Question : Simplify the given expression: $\frac{\sin^2 32^{\circ}+\sin^2 58^{\circ}}{\cos^2 32^{\circ}+\cos^2 58^{\circ}}+\sin^2 53^{\circ}+\cos 53^{\circ} \sin 37^{\circ}$
Option 2: –1
Option 3: –2
Option 4: 1
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