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If sintheta+2 costheta =1 prove that 2 sin theta-cos theta =2
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If sintheta+2 costheta =1 prove that 2 sin theta-cos theta =2?
Proof: 2sinθ - cosθ = 2, given sinθ cosθ = 1/2


Step 1: Rewrite sinθ cosθ = 1/2

We can use the identity sin2θ + cos2θ = 1 to rewrite sinθ cosθ as:

sinθ cosθ = (sinθ cosθ) + (sinθ cosθ) - (sin2θ + cos2θ)

Expanding the right-hand side of this equation, we get:

sinθ cosθ = 2(sinθ cosθ - sin2θ - cos2θ)

Using the given equation sinθ cosθ = 1/2, we can substitute and simplify to get:

1/2 = 2(1/2 - sin2θ - cos2θ)

1/4 = 1 - 2sin2θ - 2cos2θ


Step 2: Rewrite 2sinθ - cosθ

Now we can rewrite 2sinθ - cosθ as:

2sinθ - cosθ = 2(sinθ cosθ + sinθ cosθ) - cosθ

Using the given equation sinθ cosθ = 1/2, we can substitute and simplify to get:

2sinθ - cosθ = (sinθ + cosθ) + (sinθ + cosθ) - cosθ

2sinθ - cosθ = 2sinθ + 2cosθ - cosθ

2sinθ - cosθ = 2sinθ + cosθ


Step 3: Substitute sinθ cosθ = 1/2

Now we can substitute sinθ cosθ = 1/2 into our rewritten expression for 2sinθ - cosθ:

2sinθ - cosθ = 2(sinθ cosθ) + cosθ

2sinθ - cosθ = 1 + cosθ


Step 4: Use given equation sin2θ + cos2θ = 1

Finally, we can use the given equation sinθ 2 cosθ = 1 to rewrite cosθ as:

cosθ = 1/sinθ 2

Substituting this expression for cosθ into our previous equation, we get:

2sinθ - cosθ = 1 + 1/sinθ 2

2sinθ - 1/sinθ 2 = 2

Multiplying both sides by sinθ 2, we get:

2(sin2θ - 1) = 2sinθ 2

2sin2θ - 4 = 0

sin2θ = 2


Step 5: Conclusion

We have shown that if sinθ cosθ = 1/2, then 2sinθ - cosθ
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If sintheta+2 costheta =1 prove that 2 sin theta-cos theta =2?
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