Solve 11 no. Please..

Dear Student,

Please find below the solution to the asked query:

$$\begin{gathered} \Rightarrow {\mathrm{sin\theta }}_1+{\mathrm{sin\theta }}_2+{\mathrm{sin\theta }}_3=3 , 0°<{\mathrm{\theta }}_1,{\mathrm{\theta }}_2 , {\mathrm{\theta }}_3\le 90° \\ \mathrm{As} \mathrm{we} \mathrm{know} \mathrm{Sin} \mathrm{has} \mathrm{maximum} \mathrm{value} 1 \\ \mathrm{So} \mathrm{there} \mathrm{is} \mathrm{only} \mathrm{one} \mathrm{possibility} \mathrm{that} \mathrm{is} 1+1+1=3 \\ \mathrm{Hence} \\ \Rightarrow {\mathrm{\theta }}_1={\mathrm{\theta }}_2={\mathrm{\theta }}_3=1 \\ \mathrm{So} \\ \Rightarrow {\mathrm{cos\theta }}_1+{\mathrm{cos\theta }}_2+{\mathrm{cos\theta }}_3 \\ \Rightarrow \cos 90°+\cos 90°+\cos 90° \\ \Rightarrow 0+0+0 \\ \Rightarrow 0 \mathrm{Answer} \end{gathered}$$

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