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3-1.Vectors
hard
સદિશ $\mathop {\rm{P}}\limits^ \to $ $ \alpha, \beta $ અને $ \gamma $ સાથે અનુક્રમે $ X, Y$ અને $Z$ ખૂણા બનાવે છે.તો $ {sin^2}\alpha + {sin^2} \beta + {sin^2} \gamma $ =
A$0$
B$1$
C$2$
D$3$
Solution
(c)${\sin ^2}\alpha + {\sin ^2}\beta + {\sin^2} \gamma $
$ = 1 – {\cos ^2}\alpha + 1 – {\cos ^2}\beta + 1 – {\cos ^2}\gamma $
$ = 3 – ({\cos ^2}\alpha + {\cos ^2}\beta + {\cos ^2}\gamma )$
$ = 3 – 1 = 2$
$ = 1 – {\cos ^2}\alpha + 1 – {\cos ^2}\beta + 1 – {\cos ^2}\gamma $
$ = 3 – ({\cos ^2}\alpha + {\cos ^2}\beta + {\cos ^2}\gamma )$
$ = 3 – 1 = 2$
Standard 11
Physics
