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Maths Question 1 – JEE-MAIN 2025

If for θ∈[−π3,0], the points (x,y)=(3tan⁡(θ+π3),2tan⁡(θ+π6)) lie on xy+αx+βy+γ=0, then α2+β2+γ2 is equal to

Identify the relationship between the arguments of the tangent functions to simplify the expressions for x and y.

Step 1: Express x and y in terms of tangent functions and find their relationship✦ Active

Let A=θ+π3 and B=θ+π6. From the given information, we have x=3tan⁡A and y=2tan⁡B. Observe the difference between the angles A and B:

A−B=(θ+π3)−(θ+π6)=π3−π6=π6

Now, apply the tangent function to this difference:

tan⁡(A−B)=tan⁡(π6)=13
Step 2: Apply the tangent subtraction formula and substitute x and y○ Expand

Using the tangent subtraction formula tan⁡(A−B)=tan⁡A−tan⁡B1+tan⁡Atan⁡B, and substituting tan⁡A=x3 and tan⁡B=y2:

x3−y21+x3⋅y2=13

Simplify the expression:

2x−3y61+xy6=13⟹2x−3y6+xy=13
💡 Teacher's Secret Hint

Ensure careful algebraic manipulation to avoid sign errors.

Step 3: Rearrange the equation to find α,β,γ and calculate α2+β2+γ2○ Expand

Cross-multiply and rearrange the equation to match the form xy+αx+βy+γ=0:

3(2x−3y)=6+xy ⟹23x−33y=6+xy ⟹xy−23x+33y+6=0

Comparing this with the given equation xy+αx+βy+γ=0, we identify the coefficients:

α=−23 β=33 γ=6

Finally, calculate α2+β2+γ2:

α2=(−23)2=4×3=12 β2=(33)2=9×3=27 γ2=62=36 α2+β2+γ2=12+27+36=75
💡 Teacher's Secret Hint

Double-check the squaring of terms involving square roots.

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