Sarthaks Test
+3 votes
2.5k views
in JEE by (128k points)

(1)-3/5
(2) 1/3
(3) 2/9
(4) -7/9

Please log in or register to answer this question.

1 Answer

+4 votes
by (15.0k points)

Answer is -7/9

5 (tan2x - cos2x) = 2cos2x +9 

5 ( (sec2x - 1) - cos2x) = 2(2cos2x - 1) +9 

5 (1/cos2x - 1- cos2x) = 4cos2x - 2 + 9 

5 (1 - cos2x - cos4x ) = 4cos4x + 7cos2

You solve this we get = 9cos4x+12cos2x-5 

Therefore let cos4x =y2 and cos2x = y. 

0=9y2 + 12y - 5

You will get the answer by solving for y

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...