Hi friends the problem is - https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-snc6/s480x480/6405_2656465868185_1414230035_n.jpg Attempt - As per the problem states, For the first second equation of SHM, (using x = A sin ωt) a = A sin ω From here I get, sin ω = a/ A --------------(1) Using it for the 2 seconds, total displacement would be a + b. So, a + b = A sin 2ω i.e. a + b = 2A sin ω. cos ω i.e. a + b = 2A sin ω. √1-sin2ω ----------------(2) Solving both the equations, I am getting the result, A = 2a2/ √(3a2 - b2 - 2ab) But the correct answer of this problem is option (A) as per the question. Please friends help me in solving this Problem. Thank you all in advance.