Skip to content
dronacharya.ai
← JEE Advanced 2026 · Paper 2
MathematicsNumerical+2Question 15 of 54

JEE Advanced 2026 · Paper 2, Mathematics question 15

Passage

Question Stem for Question Nos. 15 and 16

Consider the curve C1C_1 given by
y=e−xfor x∈[0,10π],y=e^{-x}\qquad\text{for }x\in[0,10\pi],
and the curve C2C_2 given by
y=e−x(sin⁡x+cos⁡x)for x∈[0,10π].y=e^{-x}(\sin x+\cos x)\qquad\text{for }x\in[0,10\pi].
Let nn be the total number of points of intersection of the curves C1C_1 and C2C_2.

Suppose that α1,α2,…,αn∈[0,10π]\alpha_1,\alpha_2,\dots,\alpha_n\in[0,10\pi] are the xx-coordinates of the points of intersection of the curves C1C_1 and C2C_2 such that
α1<α2<⋯<αn.\alpha_1<\alpha_2<\dots<\alpha_n.

The value of nn is ________.

Answer and worked solution

Official answer: 11

The curves meet where sin⁡x+cos⁡x=1\sin x+\cos x=1, i.e. 2sin⁡(x+π4)=1\sqrt2\sin\left(x+\frac\pi4\right)=1:
x=2kπorx=π2+2kπ.x=2k\pi\quad\text{or}\quad x=\frac\pi2+2k\pi.
In [0,10π][0,10\pi]: x=0,2π,…,10πx=0,2\pi,\dots,10\pi (6 points) and x=π2,5π2,…,17π2x=\frac\pi2,\frac{5\pi}2,\dots,\frac{17\pi}2 (5 points).

n=11n=11.