1.

If sin (x + y) = cos (x - y), then the value of cos2 x is:1. 32. 53. 1 / 44. 1 / 2

Answer» Correct Answer - Option 4 : 1 / 2

GIVEN:

sin (x + y) = cos (x - y)

CONCEPT USED:

sinθ1 = cosθ2 , when θ1 + θ2 = 90° 

CALCULATION:

sin (x + y) = cos (x - y)

⇒ (x + y) + (x - y) = 90° 

⇒ 2x = 90° 

⇒ x = 45° 

⇒ cos2x = cos245° 

⇒ (1/√2)2 

⇒ 1/2

∴ cos2x  = 1/2


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