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Prove the following : cos-1(35)+cos-1(45)=π2 - Mathematics and Statistics

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प्रश्न

Prove the following:

`cos^-1(3/5) + cos^-1(4/5) = pi/(2)`

योग

उत्तर

Let `cos^-1(3/5)` = x

∴ cos x = `(3)/(5), "where"  0 < x < pi/(2)`
∴ sin x > 0

Now,

sin x = `sqrt(1 - cos^2x)`

= `sqrt(1 - 9/25)`

= `sqrt(16/25)`

= `(4)/(5)`
∴ x = `sin^-1(4/5)`

∴ `cos^-1(3/5) = sin^-1(4/5)`    ...(1)

L.H.S. = `cos^-1(3/5) + cos^-1(4/5)`

= `sin^-1(4/5) + cos^-1(4/5)`   ...[By (1)]

= `pi/(2)                      ...[∵ sin^-1x + cos^-1x = pi/2]`

= R.H.S.

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अध्याय 3: Trigonometric Functions - Exercise 3.3 [पृष्ठ १०३]

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बालभारती Mathematics and Statistics 1 (Arts and Science) [English] 12 Standard HSC Maharashtra State Board
अध्याय 3 Trigonometric Functions
Exercise 3.3 | Q 3.4 | पृष्ठ १०३

वीडियो ट्यूटोरियलVIEW ALL [3]

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