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# Prove the Following Identities, Where the Angles Involved Are Acute Angles for Which the Expressions Are Defined. ( 1 + Tan 2 a 1 + Cot 2 a ) = ( 1 − Tan a 1 − Cot a ) 2 = Tan 2 a - Mathematics

Sum

Prove the following identities, where the angles involved are acute angles for which the expressions are defined.

((1+tan^2A)/(1+cot^2A))=((1-tanA)/(1-cotA))^2=tan^2A

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#### Solution

((1+tan^2A)/(1+cot^2A))=((1-tanA)/(1-cotA))^2=tan^2A

(1+tan^2A)/(1+cot^2A)=(1+sin^2A/cos^2A)/(1+cos^2A/sin^2A)=((cos^2A+sin^2A)/cos^2A)/((sin^2A+cos^2A)/sin^2A)

=(1/cos^2A)/(1/sin^2A)=sin^2A/cos^2A

=tan^2A

((1-tanA)/(1-cotA))^2=(1+tan^2A-2tanA)/(1+cot^2A-2cotA)

=(sec^2A-2tanA)/(cosec^2A-2cotA)

=(1/cos^2A-(2sinA)/cosA)/(1/sin^2A-(2cosA)/sinA)=((1-2sinAcosA)/cos^2A)/((1-2sinAcosA)/sin^2A)

=sin^2A/cos^2A=tan^2A

Concept: Trigonometry
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#### APPEARS IN

NCERT Class 10 Maths
Chapter 8 Introduction to Trigonometry
Exercise 8.4 | Q 5.1 | Page 194
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