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If sinθ = (m2 – n2)/(m2 + n2) and 0 < θ < π/2, then what is the value of cosθ?
  • a)
    2mn/(m2 + n2)
  • b)
    2mn/(m2 - n2)
  • c)
    (m2 + n2)/2mn
  • d)
    (m2 - n2)/2mn
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
If sinθ = (m2– n2)/(m2+ n2) and 0 < θ < π/2...
sinθ = (m2 – n2)/(m2 + n2)
Squaring on both the sides
Sin2θ = (m2 – n2)2/(m2 + n2)2 [∵ (a – b)2 = (a + b)2 – 4ab]
Sin2θ = [(m2 + n2)2 – 4m2n2]/(m2 + n2)2 [∵ (a – b)2 = (a + b)2 – 4ab]
Sin2θ = 1 – 4m2n2/(m2 + n2)2
4m2n2/(m2 + n2)2 = 1 – sin2θ
4m2n2/(m2 + n2)2 = cos2θ [∵ sin2θ + cos2θ = 1]
Taking the square roots
∴ 2mn/(m2 + n2) = cosθ
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Most Upvoted Answer
If sinθ = (m2– n2)/(m2+ n2) and 0 < θ < π/2...
Given Information:
- sinθ = (m2– n2)/(m2+ n2)
- 0 < θ="" />< />

To Find:
Value of cosθ

Solution:

Step 1: Use the trigonometric identity sin^2θ + cos^2θ = 1

Step 2: Substitute sinθ from the given information
(sinθ)^2 + cos^2θ = 1
[(m2– n2)/(m2+ n2)]^2 + cos^2θ = 1
(m2– n2)^2/(m2+ n2)^2 + cos^2θ = 1

Step 3: Simplify the equation
(m2 - n2)^2 + cos^2θ * (m2 + n2)^2 = (m2 + n2)^2
(m2 - n2)^2 + cos^2θ * (m2 + n2)^2 = m2^2 + 2mn + n2^2

Step 4: Solve for cos^2θ
cos^2θ = (m2^2 + 2mn + n2^2 - (m2 - n2)^2)/(m2 + n2)^2
cos^2θ = (4m^2n^2)/(m2 + n2)^2
cosθ = 2mn/(m2 + n2) (Taking square root on both sides)
Therefore, the value of cosθ is option A) 2mn/(m2 + n2).
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If sinθ = (m2– n2)/(m2+ n2) and 0 < θ < π/2, then what is the value of cosθ?a)2mn/(m2+ n2)b)2mn/(m2- n2)c)(m2+ n2)/2mnd)(m2- n2)/2mnCorrect answer is option 'A'. Can you explain this answer?
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