Question 12
If sin A + sin2 A = 1, then the value of the expression (cos2 A + cos4 A) is
(A) 1 (B) 1/2 (C) 2 (D) 3
Given
sin A + sin2 A = 1
sin A = 1 − sin2 A
sin A = cos2 A
Now,
cos2 A + cos4 A
= cos2 A + (cos2 A) 2
Putting cos2 A = sin A
= sin A + sin2 A
Given sin A + sin2 A = 1
= 1
So, the correct answer is (A)
Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.
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