All Exams Test series for 1 year @ ₹349 only
Question

ABC is a right-angled triangle, right angled at C. If A = 60° and AC = $20\sqrt{3}$ units, then find AB.

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
$40\sqrt{3}$ units

Triangle Problem Setup

We are analyzing a right-angled triangle named ABC, where angle C is the right angle (90°).

  • Given Angle A = 60°
  • Given side AC (adjacent to Angle A) = $20\sqrt{3}$ units
  • The goal is to find the length of the hypotenuse AB.

Trigonometry Application

In a right-angled triangle, the cosine function relates the angle, the adjacent side, and the hypotenuse:

$cos(Angle) = Adjacent / Hypotenuse$

Applying this to Angle A:

$\cos(A) = \frac{AC}{AB}$

Calculation Steps

Substitute the known values into the formula:

$\cos(60^\circ) = \frac{20\sqrt{3}}{AB}$

Recall the value of $\cos(60^\circ)$, which is $\frac{1}{2}$.

So, the equation becomes:

$\frac{1}{2} = \frac{20\sqrt{3}}{AB}$

Rearrange the equation to solve for AB:

$AB = 2 \times 20\sqrt{3}$

$AB = 40\sqrt{3}$

Result

The length of the hypotenuse AB is $40\sqrt{3}$ units.

Was this answer helpful?

Similar Questions

  1. If $r\sin\theta = \frac{7}{2}$ and $r\cos\theta = \frac{7\sqrt{3}}{2}$, then what will be the value of r?
  2. If $\sin(3x - 20)^\circ = \cos(20 - 3y)^\circ$, then value of x - y will be:
  3. If $\sin \theta + \text{cosec } \theta = \sqrt{5}$, then the value of $\sin^3 \theta + \text{cosec}^3 \theta$ is:
  4. If $x + y = 75$ and $\sin x : \sin y = \frac{1}{\sqrt{2}} : \frac{1}{2}$, then $x : y$ is:
  5. If $(1 + \tan A)(1 + \tan B) = 2$, then what will be the value of $\tan(A+B)$?
  6. The value of $\frac{\tan 45^\circ - \tan 30^\circ}{1 + \tan 45^\circ \tan 30^\circ}$ is :
  7. Angle $54^\circ$ is equivalent to (in radians):
  8. If $\cos x=-\frac{3}{5}$ and $x$ lies in the third quadrant, then the value of the $\sin x$ is:
  9. If $\sin(x - y) = \frac{\sqrt{3}}{2}$ and $\cos(x + y) = \frac{1}{2}$, where x and y are positive acute angles and $x \ge y$, then the value of $x$ is:
  10. If $\sin\theta - \cos\theta = \frac{\sqrt{3}}{2}$, then find the positive value of $\sin\theta + \cos\theta$.

Important Questions from Trigonometry

  1. The given equation can be reduced to

  2. If sin2x = a - b√c, where a and b are natural numbers and c is prime number, then what is the value of a - b + 2c ?

  3. Let θ be a positive angle. If the number of degrees in θ is divided by the number of radians in θ, then an irrational number 180 / π results. If the number of degrees in θ is multiplied by the number of radians in θ, then an irrational number 125π / 9 results. The angle θ must be equal to

  4. What is sin 2α equal to?

  5. If \(\sin θ = \frac{8}{{17}}\) , then find the value of tan θ. 

Need Expert Advice?
Upcoming Exams
RRB ALP
July 28, 2026
RRB Group D
August 03, 2026
Test Series
RRB NTPC img
Railways
RRB NTPC Under Graduate 2026 New Mock Test Series
1459 Tests 2 Tests Free
215 Attempts
4.3(512)
English, Hindi, Telugu +7 More

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App