JEE · Maths doubts
233 doubts found
I keep getting “Argand plane” questions wrong in Complex Numbers. What's the trap?
plotting the imaginary part on the x-axis.
I keep getting “Infinite geometric series” questions wrong in Sequences & Series. What's the trap?
applying the sum formula when |r| ≥ 1.
I keep getting “Fundamental principle of counting” questions wrong in Permutations & Combinations. What's the trap?
adding when you should multiply independent choices.
I keep getting “Middle term” questions wrong in Binomial Theorem. What's the trap?
assuming there's always exactly one middle term.
I keep getting “Range of sine and cosine” questions wrong in Trigonometry. What's the trap?
accepting an answer where sinθ > 1.
I keep getting “Equation forms” questions wrong in Straight Lines. What's the trap?
picking a form that doesn't match the given data.
I keep getting “Standard equations” questions wrong in Conic Sections. What's the trap?
mismatching the axis of the parabola with its equation.
I keep getting “Standard limit” questions wrong in Limits & Continuity. What's the trap?
evaluating it as 0/0 and stopping.
I keep getting “Product and quotient rules” questions wrong in Differentiation. What's the trap?
differentiating a product as just u'v'.
I keep getting “Methods of integration” questions wrong in Integration. What's the trap?
reaching for by-parts when a simple substitution works.
I keep getting “Conditional probability” questions wrong in Probability. What's the trap?
assuming P(A|B) equals P(B|A).
I keep getting “Direction ratios” questions wrong in Vectors & 3D Geometry. What's the trap?
confusing direction ratios with direction cosines (which are normalised).
I keep getting “Matrix as a system solver” questions wrong in Matrices & Determinants. What's the trap?
trying to 'divide' by a matrix instead of multiplying by its inverse.
I keep getting “Critical points” questions wrong in Application of Derivatives. What's the trap?
thinking every point where f'(x)=0 is a maximum.
What does “Integral as accumulation” actually mean in Applications of Integrals, and why does it matter for JEE?
integrating a rate gives the total accumulated change (e.g. integrating velocity gives displacement).
I keep getting “Order and degree” questions wrong in Differential Equations. What's the trap?
reading the degree off a square-rooted or fractional form.
What does “Principal value branch” actually mean in Relations, Functions & Inverse Trigonometry, and why does it matter for JEE?
inverse trig functions are made single-valued by restricting their range to a principal branch (e.g. sin⁻¹ to [−π/2, π/2]).
What does “Measures of spread” actually mean in Sets & Statistics, and why does it matter for JEE?
standard deviation measures how far the data typically lie from the mean — small means tightly clustered, large means spread out.
What is the difference between real roots and complex roots?
Real roots occur when D≥0 (the parabola meets the x-axis); complex roots occur when D<0 (it doesn't).
What is the difference between real part and imaginary part?
In a+bi, a is the real part (on the x-axis) and b is the imaginary coefficient (on the y-axis).
What is the difference between arithmetic progression and geometric progression?
An AP grows by adding a fixed number each step; a GP grows by multiplying by a fixed ratio each step.
What is the difference between permutation and combination?
A permutation counts ordered arrangements (a password); a combination counts unordered selections (a team) — nCr = nPr / r!.
What is the difference between binomial coefficient and term?
The binomial coefficient nCr is just the number multiplying a term; the term itself also includes the powers of a and b.
What is the difference between degrees and radians?
Degrees split a circle into 360 parts; radians measure the arc length per unit radius (2π in a full circle) and are used in calculus.