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Grade:
        
If sin 2a + sin 2b = 1/2 and cos 2a + cos2b = 3/2, then cos^2(a-b) is equal to
(A) 3/8
(B) 5/8 [correct answer]
(C) ¾
(D) 5/4
 
Please give the solution for this question..
11 months ago

Answers : (3)

Saurabh Koranglekar
askIITians Faculty
2933 Points
							Dear Anushka Khuspe



576-1636_1.jpg

Answer is C

please find attached file

also please revert for this or similar problems

Thanks and regards
11 months ago
Anushka Khuspe
8 Points
							
Thank you for your attempt to this question. It really helped me. 
The only thing is, the rest of the solution is correct but I think that you have done some mistake in the last line of the solution (regarding the identity of trigonometry used) and by correcting that error I get the answer as 5/8...which is probably the correct answer. 
11 months ago
Saurabh Koranglekar
askIITians Faculty
2933 Points
							cos(2(a-b)) = ¼ and not ½

you are correct

thanks and keep posting

good luck,576-914_1.JPG
11 months ago
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