हिंदी

If A = [(0, –tan  α/2), (tan  α/2, 0)] and I is the identity matrix of order 2, show that I + A = (I – A)[(cos α, –sin α),(sin α, cos α)]

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प्रश्न

If A = `[(0, -tan  α/2), (tan  α/2, 0)]` and I is the identity matrix of order 2, show that I + A = `(I - A)[(cos α, -sin α),(sin α, cos α)]`

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उत्तर

A = `[(0, -tan  α/2), (tan  α/2, 0)]`, I = `[(1, 0),(0, 1)]` 

I + A = `[(1, 0),(0, 1)] + [(0, -tan  α/2), (tan  α/2, 0)]`

= `[(1, -tan  α/2), (tan  α/2, 1)]`

`(I - A) [(cos α, -sin α),(sin α, cos α)] = ([(1, 0),(0, 1)] - [(0, -tan α/2), (tan α/2, 0)]) [(cos α, -sin α),(sin α, cos α)]`

= `[(1, tan  α/2), (-tan  α/2, 1)] [(cos α, -sin α),(sin α, cos α)]` 

= `[(1, tan  α/2), (-tan  α/2, 1)]` `[((1 - tan^2  α/2)/(1 + tan^2  α/2)(-2  tan  α/2)/(1 + tan^2  α/2)),((-2 tan  α/2)/(1 + tan^2  α/2)(1 - tan^2  α/2)/(1 + tan^2  α/2))]`

= `[((1 + tan^2  α/2)/(1 + tan^2  α/2)(-tan  α/2 - tan^3  α/2)/(1 + tan^2  α/2)),((tan  α/2 + tan^3  α/2)/(1 + tan^2  α/2)(1 + tan^2  α/2)/(1 + tan^2  α/2))]`

= `[(1, -tan  α/2),(tan  α/2, 1)]`

Hence, `I + A = (I - A) [(cos α, -sin α),(sin α, cos α)]`

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अध्याय 3: Matrices - EXERCISE 3.2 [पृष्ठ ६०]

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एनसीईआरटी Mathematics Part 1 and 2 [English] Class 12
अध्याय 3 Matrices
EXERCISE 3.2 | Q 18. | पृष्ठ ६०

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