Tangents and Normals — Maths STD 12 Science — Question
Gujarat BoardEnglish MediumSTD 12 ScienceMathsTangents and Normals3 Marks
Question
Write the angle between the curves y = e-x and y = ex at their point of intersections.
✓
Answer
The given equation of curve are, y = e-x ...(1) y = ex ...(2) Solving (1) and (2) $\text{y}=\frac{1}{\text{e}^\text{x}}=\frac{1}{\text{y}}$ $\Rightarrow\text{y}^2=1$ $\Rightarrow\text{y}=\pm1$ From (2) $\pm1=\text{e}^\text{x}$ $\Rightarrow\text{x}=0$ So, the point of intersection is P = (0, 1) and Q = (0, -1). Slope of (2) $\text{m}_2=\frac{\text{dy}}{\text{dx}}=\text{e}^{\text{x}}$ $\therefore\text{m}_2\text{ at }\text{P}=1\text{ and }\text{m}_2\text{ at }\text{Q}=1$ $\therefore\text{m}_1\times\text{m}_2=-1\times1=-1$ The angle between the curves is 90º
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