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Evaluate: 2(tan35∘cot55∘)2+(cot55∘tan35∘)2-3(sec40∘cosec50∘) - Mathematics

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Question

Evaluate:

`2(tan35^@/cot55^@)^2 + (cot55^@/tan35^@)^2 - 3(sec40^@/(cosec50^@))`

Evaluate

Solution

`2(tan35^@/cot55^@)^2 + (cot55^@/tan35^@)^2 - 3(sec40^@/(cosec50^@))`

= `2(tan(90^@-55^@)/cot55^@)^2 + (cot(90^@-35^@)/tan35^@)^2 - 3(sec(90^@-50^@)/(cosec50^@))`

= `2(cot55^@/cot55^@)^2 + (tan35^@/tan35^@)^2 - 3((cosec50^@)/(cosec50^@))`  ...`[∵ tan (90^@ - theta) = cot theta`  `cot(90^@ - theta) = tan theta` ` sec(90^@ - theta) = cosec theta`]

= 2 × (1)2 + (1)2 – 3 × 1

= 2 × 1 + 1 – 3

= 2 + 1 – 3

= 0

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Chapter 21: Trigonometrical Identities - Exercise 21 (E) [Page 332]

APPEARS IN

Selina Mathematics [English] Class 10 ICSE
Chapter 21 Trigonometrical Identities
Exercise 21 (E) | Q 7.1 | Page 332
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