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Trigonometric Functions appeared 27 times across 3 years — 3.1% of Mathematics. This question is from Trigonometric Identities.

Year 2026 2025 2024 Total
Questions 10 10 7 27

If x + ² x = 1, x in (0, (π)/(2)), then ( ¹² x + ¹² x) + 3 ( ¹⁰ x + ¹⁰ x + ⁸ x + ⁸ x) + ( ⁶ x + ⁶ x) is equal to

Solution & Explanation

Related Formula

Fundamental identities:

² x + ² x = 1 x = ( x)/( x)

Algebraic identity for a perfect cube:

(A + B)³ = A³ + 3A²B + 3AB² + B³
Core Logic

Given equation:

x + ² x = 1 x = 1 - ² x = ² x

Dividing both sides by ² x:

( x)/( ² x) = 1 x x = 1 x = x
Step 1: Simplify the Expression

Since x = x, we can substitute x with x throughout the given expression:

( ¹² x + ¹² x) + 3( ¹⁰ x + ¹⁰ x + ⁸ x + ⁸ x) + ( ⁶ x + ⁶ x) = 2 ¹² x + 6 ¹⁰ x + 6 ⁸ x + 2 ⁶ x = 2[ ¹² x + 3 ¹⁰ x + 3 ⁸ x + ⁶ x]
Step 2: Apply the Cubic Identity

Notice that the expression inside the brackets matches the expansion of a perfect cube:

= 2[( ⁴ x + ² x)³]

Since ² x = x, it follows that ⁴ x = ² x. Substituting these back in:

= 2[( ² x + x)³]

We know from the problem statement that x + ² x = 1. Therefore:

= 2(1)³ = 2

Pattern Recognition

When given x + ² x = 1, the substitution ² x = x or x = x is a classic identity trick. Recognizing binomial coefficients (1, 3, 3, 1) immediately signals to condense into a full cube structure.

Chapter Mix

Class 11 Mathematics: Trigonometric Functions

Reference Study Guides

More Trigonometric Functions Previous-Year Questions

Q18 jee_main_2026_21_jan_morning Transformation Formulas
The value of 10° - √(3) 10° is equal to:
  • A. 4
  • B. 2
  • C. 8
  • D. 6

Solution

Related Formula
(A - B) = A B - A B 2A = 2 A A
Core Logic
10° - √(3) 10° = 1 10° - √(3) 10° = 10° - √(3) 10° 10° 10°
Step 1: Sine Transformation

Multiply and divide the numerator by 2 to inject standard trig values:

= 2 ((1)/(2) 10° - √(3)2 10°) 10° 10°

Substitute 30° = 1/2 and 30° = √(3)/2:

= 2 ( 30° 10° - 30° 10°) 10° 10°
Step 2: Apply Multiple Angle identities

The numerator becomes 2 (30° - 10°) = 2 20°. Multiply and divide the denominator by 2 to construct 2θ:

= 4 20°2 10° 10° = 4 20° 20°

= 4

Pattern Recognition

Any expression structured as A θ - B θ instantly signals a fraction collapse to 2 (α - θ) / (2θ) via multiplication by 2. When constants are 1 and √(3), the anchor is always 30° or 60°.

Chapter Mix

Class 11 Maths: Trigonometric Functions

Q24 jee_main_2026_22_january_morning Trigonometric Identities
If ²48°- ²12° ²24°- ²6°= α+β√(5)2, where α,βin N, then α+β is equal to ____.
Numerical Answer. Answer: 4 to 4

Solution

Related Formula
(A+B) (A-B) = ² A - ² B (A+B) (A-B) = ² A - ² B
Core Logic

Evaluate numerator: ² 48^° - ² 12^° Let A = 48^° and B = 12^°. Using the identity: (48^° + 12^°) (48^° - 12^°) = 60^° 36^°

Evaluate denominator: ² 24^° - ² 6^° Let A = 24^° and B = 6^°. Using the identity: (24^° + 6^°) (24^° - 6^°) = 30^° 18^°

Step 1: Substituting Standard Trigonometric Values

We need standard values: 60^° = (1)/(2) 36^° = √(5) + 14 30^° = (1)/(2) 18^° = √(5) - 14

Substitute into the expression:

( 60^° 36^°)/( 30^° 18^°) = (1/2) · ( √(5) + 14) (1/2) · ( √(5) - 14)
Step 2: Rationalizing the Denominator
= √(5) + 1√(5) - 1

Rationalize by multiplying numerator and denominator by (√(5) + 1):

= (√(5) + 1)²(√(5))² - 1² = 5 + 1 + 2√(5)5 - 1 = 6 + 2√(5)4 = 3 + √(5)2
Step 3: Final Mapping

Comparing 3 + √(5)2 to the given form α + β√(5)2:

α = 3 β = 1

Both are natural numbers. Their sum is α + β = 3 + 1 = 4.

Pattern Recognition

Difference of squares of sines/cosines is a massive neon sign to use product-to-sum composite identities. Always commit 18^° and 36^° to memory as they form complementary golden ratio components in geometry and algebra.

Chapter Mix

Class 11 Maths: Trigonometric Functions

Q23 jee_main_2026_22_january_evening Compound Angles and Tangent Identities
Let (α + β) = -(1)/(10) and (α - β) = (3)/(8), where 0 < α < (π)/(3) and 0 < β < (π)/(4). If 2α = 3(1 - r√(5))√(11)(s + √(5)), r, s in N, then r + s is equal to ____.
Numerical Answer. Answer: 20 to 20

Solution

Related Formula

Tangent sum formula:

2α = [(α + β) + (α - β)] = ( (α + β) + (α - β))/(1 - (α + β) (α - β))
Core Logic

Given (α + β) = -(1)/(10) (α + β) = -√(99) = -3√(11). Given (α - β) = (3)/(8) (α - β) = 3√(55) = 3√(5)√(11).

Step 1: Simplify Tangent of 2 Alpha
2α = -3√(11) + 3√(5)√(11)1 + 3√(11) · 3√(5)√(11) = -3√(55) + 3√(55) √(5) + 9√(5) = 3(1 - 11√(5))√(11)(9 + √(5))
Step 2: Compare Constants

Comparing with 3(1 - r√(5))√(11)(s + √(5)):

r = 11, s = 9 r + s = 20
Pattern Recognition

Express 2α as (α+β) + (α-β) to apply standard compound tangent formula directly.

Chapter Mix

Class 11 Maths: Trigonometry

Q16 jee_main_2026_23_january_morning Trigonometric Equations
Number of solutions of √(3) 2θ+8 θ+3√(3)=0, θ in [-3π,2π] is:
  • A. 0
  • B. 5
  • C. 3
  • D. 4

Solution

Related Formula
2θ = 2 ²θ - 1
Core Logic

Substitute the double-angle formula into the given equation to form a quadratic in θ:

√(3)(2 ²θ - 1) + 8 θ + 3√(3) = 0 2√(3) ²θ + 8 θ + 2√(3) = 0
Step 1: Solve the Quadratic

Factorize the quadratic equation:

2√(3) ²θ + 2 θ + 6 θ + 2√(3) = 0

Wait, 2 × 2√(3) = 12. The factors of 12 that sum to 8 are 6 and 2.

2 θ(√(3) θ + 1) + 2√(3)(√(3) θ + 1) = 0 (√(3) θ + 1)(2 θ + 2√(3)) = 0

This gives:

θ = - 1√(3) or θ = -√(3)

Since -1 ≤ θ ≤ 1, we reject θ = -√(3).

Step 2: Count Solutions in Interval

We need solutions for θ = - 1√(3) in the interval [-3π, 2π]. The period of cosine is 2π. The equation θ = k (where -1 < k < 0) has 2 solutions per 2π interval. Intervals: [0, 2π]: 2 solutions (in Quadrants II and III). [-2π, 0]: 2 solutions. [-3π, -2π]: 1 solution (in Quadrant II equivalent, which is Quadrant III when going backwards. Specifically, from -3π to -2π covers the top half of the circle. Wait, [-3π, -2π] goes from 180^° to 360^° logically, i.e., quadrants III and IV. is negative in Quadrant III. So exactly 1 solution). Total solutions = 2 + 2 + 1 = 5.

Pattern Recognition

Mapping phase intervals chunk by chunk (2π cycles yield 2 roots for | x|<1) prevents overcounting when domain bounds don't cleanly align with full periods.

Chapter Mix

Class 11 Maths: Trigonometric Functions

Q18 jee_main_2026_23_january_morning Maximum and Minimum Values
Let α and β respectively be the maximum and the minimum values of the function f(θ) = 4( ⁴((7π)/(2) -θ) + ⁴ (11π +θ)) -2( ⁶((3π)/(2) -θ) + ⁶ (9π -θ)), θ in R. Then α + 2β is equal to :
  • A. 4
  • B. 5
  • C. 3
  • D. 6

Solution

Related Formula
⁴θ + ⁴θ = 1 - 2 ²θ ²θ ⁶θ + ⁶θ = 1 - 3 ²θ ²θ
Core Logic

First, simplify the trigonometric arguments by reducing angles: ((7π)/(2) - θ) = - θ (11π + θ) = - θ ((3π)/(2) - θ) = - θ (9π - θ) = θ

Step 1: Simplify the Function

Substitute these back into f(θ):

f(θ) = 4( ⁴θ + ⁴θ) - 2( ⁶θ + ⁶θ)

Applying the algebraic identities:

f(θ) = 4(1 - 2 ²θ ²θ) - 2(1 - 3 ²θ ²θ) f(θ) = 4 - 8 ²θ ²θ - 2 + 6 ²θ ²θ f(θ) = 2 - 2 ²θ ²θ
Step 2: Convert to Double Angle

Multiply and divide the second term by 2 to use (2θ):

f(θ) = 2 - (4 ²θ ²θ)/(2) = 2 - ( ²(2θ))/(2)
Step 3: Find Maximum and Minimum

Since 0 ≤ ²(2θ) ≤ 1: Max value (α): Occurs when ²(2θ) = 0. α = 2 - 0 = 2. Min value (β): Occurs when ²(2θ) = 1. β = 2 - (1)/(2) = (3)/(2).

Step 4: Evaluate the Target Expression

We need α + 2β:

= 2 + 2((3)/(2)) = 2 + 3 = 5
Pattern Recognition

The expression a( ⁴ x + ⁴ x) - b( ⁶ x + ⁶ x) is a ubiquitous JEE template. Immediately swap to (1-2 ² x ² x) and (1-3 ² x ² x) for mass cancellation.

Chapter Mix

Class 11 Maths: Trigonometric Functions

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