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Question 6 - CBSE Class 10 Sample Paper for 2018 Boards - Solutions of Sample Papers for Class 10 Boards

Last updated at July 27, 2026 by

If cos A = 2/5 , find the value of 4 + 4 tan 2 A

This is a question of CBSE Sample Paper - Class 10 - 2017/18.

You can download the question paper here  https://www.teachoo.com/cbse/sample-papers/

If cos A = 2/5 , find the value of 4 + 4 tan^2 A - Teachoo

Question 6 - CBSE Class 10 Sample Paper for 2018 Boards - Part 2
Question 6 - CBSE Class 10 Sample Paper for 2018 Boards - Part 3

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Transcript

Question 6 If cos A = 2/5 , find the value of 4 + 4 tan2 A Given cos A = 2/5 (š‘†š‘–š‘‘š‘’ š‘Žš‘‘š‘—š‘Žš‘š‘’š‘›š‘” š‘”š‘œ āˆ š“)/š»š‘¦š‘š‘œš‘”š‘’š‘›š‘¢š‘ š‘’ = 2/5 š“šµ/š“š¶=2/5 Let AB = 2x & AC = 5x Using Pythagoras theorem to find BC (Hypotenuse)2 = (Height)2 + (Base)2 AC2 = AB2 + BC2 (5x)2 = (2x)2 + (BC)2 (BC)2 = (5x)2 - (2x)2 (BC) 2 = 25x2 ā€“ 4x2 (BC) 2 = 21x2 BC = āˆš(21š‘„^2 ) BC = āˆš21 š‘„ Now, tan A = (š‘†š‘–š‘‘š‘’ š‘œš‘š‘š‘œš‘ š‘–š‘”š‘’ š‘”š‘œ āˆ š“)/(š‘†š‘–š‘‘š‘’ š‘Žš‘‘š‘—š‘Žš‘š‘’š‘›š‘” š‘”š‘œ āˆ š“) tan A = šµš¶/š“šµ tan A = (āˆš21 š‘„)/2š‘„ tan A = āˆš21/2 Thus, 4 + 4 tan2 A = 4 + 4 (āˆš21/2)^2 = 4 + 4 Ɨ 21/4 = 4 + 21 = 25

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