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/
Last updated at Sept. 24, 2021 by Teachoo
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/
Transcript
Question 6 If cos A = 2/5 , find the value of 4 + 4 tan2 A Given cos A = 2/5 (๐๐๐๐ ๐๐๐๐๐๐๐๐ก ๐ก๐ โ ๐ด)/๐ป๐ฆ๐๐๐ก๐๐๐ข๐ ๐ = 2/5 ๐ด๐ต/๐ด๐ถ=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 โ 4x2 (BC) 2 = 21x2 BC = โ(21๐ฅ^2 ) BC = โ21 ๐ฅ Now, tan A = (๐๐๐๐ ๐๐๐๐๐ ๐๐ก๐ ๐ก๐ โ ๐ด)/(๐๐๐๐ ๐๐๐๐๐๐๐๐ก ๐ก๐ โ ๐ด) tan A = ๐ต๐ถ/๐ด๐ต tan A = (โ21 ๐ฅ)/2๐ฅ tan A = โ21/2 Thus, 4 + 4 tan2 A = 4 + 4 (โ21/2)^2 = 4 + 4 ร 21/4 = 4 + 21 = 25
CBSE Class 10 Sample Paper for 2018 Boards
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CBSE Class 10 Sample Paper for 2018 Boards
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