Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class


Ex 3.3, 12 If A = [β– 8(cos 𝛼&γ€–βˆ’sin〗⁑𝛼@sin⁑𝛼&cos⁑𝛼 )] , then A + A’ = I , if the value of Ξ± is A. 𝛑/πŸ” B. 𝛑/πŸ‘ C. Ο€ D. πŸ‘π›‘/𝟐 A = [β– 8(cos⁑𝛼&γ€–βˆ’sin〗⁑𝛼@sin⁑𝛼&cos⁑𝛼 )] A’= [β– 8(cos⁑𝛼&sin⁑𝛼@γ€–βˆ’sin〗⁑𝛼&cos⁑𝛼 )] and I = [β– 8(1&0@0&1)] Given A + A’ = I [β– 8(𝐜𝐨𝐬⁑𝜢&γ€–βˆ’π¬π’π§γ€—β‘πœΆ@𝐬𝐒𝐧⁑𝜢&𝐜𝐨𝐬⁑𝜢 )] + [β– 8(𝐜𝐨𝐬⁑𝜢&𝐬𝐒𝐧⁑𝜢@γ€–βˆ’π¬π’π§γ€—β‘πœΆ&𝐜𝐨𝐬⁑𝜢 )] = [β– 8(𝟏&𝟎@𝟎&𝟏)] [β– 8(cos⁑〖𝛼+cos⁑𝛼 γ€—&γ€–βˆ’sin〗⁑〖𝛼+sin⁑𝛼 γ€—@sin⁑𝛼 γ€–βˆ’sin〗⁑𝛼&cos⁑〖𝛼+cos⁑𝛼 γ€— )]= [β– 8(1&0@0&1)] [β– 8(𝟐𝐜𝐨𝐬⁑𝜢&𝟎@𝟎&𝟐𝐜𝐨𝐬⁑𝜢 )]= [β– 8(𝟏&𝟎@𝟎&𝟏)] Since the matrices are equal, corresponding elements are equal 2cos 𝜢 = 1 cos⁑𝛼 = 1/2 cos⁑𝛼 = cos⁑〖60Β°γ€— Comparing angles 𝛼 = 60Β° 𝛼 = 60Β° Γ— πœ‹/(180Β°) 𝜢 = 𝝅/πŸ‘ So the correct answer is (B)

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Davneet Singh

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.