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MAXIMUM value of sin^2(120+theta)+sun^2(120-theta) is

MAXIMUM value of sin^2(120+theta)+sun^2(120-theta) is
 

Grade:12th pass

2 Answers

Saurabh Koranglekar
askIITians Faculty 10335 Points
5 years ago
576-1579_1.PNG
Arun
25750 Points
5 years ago
sin(t)^2 = (1/2) * (1 - cos(2t)) 

sin(120 + a)^2 + sin(120 - a)^2 => 
(1/2) * (1 - cos(2 * (120 + a))) + (1/2) * (1 - cos(2 * (120 - a))) => 
(1/2) * (1 - cos(240 + 2a) + 1 - cos(240 - 2a)) => 
(1/2) * (2 - (cos(240 + 2a) + cos(240 - 2a))) => 
1 - (1/2) * (cos(240)cos(2a) - sin(240)sin(2a) + cos(240)cos(2a) + sin(240)sin(2a)) => 
1 - (1/2) * (2 * cos(240) * cos(2a)) => 
1 - cos(240) * cos(2a) 

cos(t) = 1 when t = 360 * k 
cos(t) = -1 when t = 180 + 360 * k 

1 - cos(240) * (-1) => 
1 + cos(240) => 
1 - 1/2 => 
1/2 

1 - cos(240) * 1 => 
1 - (-1/2) => 
3/2 

3/2 is the maximum

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