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Question

In $\triangle\text{ABC}$, $\text{BD} \perp \text{AC}$ at $\text{D}$ and $\angle\text{DBC} = 60^{\circ}$. $\text{E}$ is a point on $\text{BC}$ such that $\angle\text{CAE} = 20^{\circ}$. What is the measure of $\angle\text{AEB}$?

This question was previously asked in
RRB NTPC 2024 CBT 1 Question Paper (28-Aug-2025) (Shift 3)
The correct answer is
$50^{\circ}$

The problem asks for the measure of angle AEB in a triangle ABC with specific conditions.

Geometric Analysis of Triangle ABC

We are given a triangle ABC where BD is perpendicular to AC at point D. This means $\angle\text{BDC} = 90^{\circ}$.

We are also given that $\angle\text{DBC} = 60^{\circ}$.

Calculating Angles in Triangle BDC

Consider the right-angled triangle BDC:

  • The sum of angles in a triangle is $180^{\circ}$.
  • In $\triangle\text{BDC}$, we have $\angle\text{BDC} + \angle\text{DBC} + \angle\text{BCD} = 180^{\circ}$.
  • Substituting the known values: $90^{\circ} + 60^{\circ} + \angle\text{BCD} = 180^{\circ}$.
  • Solving for $\angle\text{BCD}$: $150^{\circ} + \angle\text{BCD} = 180^{\circ}$, which gives $\angle\text{BCD} = 180^{\circ} - 150^{\circ} = 30^{\circ}$.
  • Therefore, $\angle\text{BCA} = 30^{\circ}$.

Calculating Angles in Triangle ABC

Now, consider the larger triangle ABC:

  • The sum of angles in $\triangle\text{ABC}$ is $180^{\circ}$: $\angle\text{ABC} + \angle\text{BCA} + \angle\text{CAB} = 180^{\circ}$.
  • Substitute $\angle\text{BCA} = 30^{\circ}$: $\angle\text{ABC} + 30^{\circ} + \angle\text{CAB} = 180^{\circ}$.
  • This simplifies to $\angle\text{ABC} + \angle\text{CAB} = 150^{\circ}$.

Finding Angle AEB

We are given a point E on BC such that $\angle\text{CAE} = 20^{\circ}$. We need to find $\angle\text{AEB}$.

Consider the triangle ABE:

  • The sum of angles in $\triangle\text{ABE}$ is $180^{\circ}$: $\angle\text{AEB} + \angle\text{ABE} + \angle\text{BAE} = 180^{\circ}$.
  • Note that $\angle\text{ABE}$ is the same as $\angle\text{ABC}$.
  • The angle $\angle\text{BAE}$ can be expressed as $\angle\text{CAB} - \angle\text{CAE}$.
  • So, $\angle\text{BAE} = \angle\text{CAB} - 20^{\circ}$.
  • Substitute these into the angle sum for $\triangle\text{ABE}$: $\angle\text{AEB} + \angle\text{ABC} + (\angle\text{CAB} - 20^{\circ}) = 180^{\circ}$.
  • Rearrange the terms: $\angle\text{AEB} + (\angle\text{ABC} + \angle\text{CAB}) - 20^{\circ} = 180^{\circ}$.
  • We already found that $\angle\text{ABC} + \angle\text{CAB} = 150^{\circ}$.
  • Substitute this value: $\angle\text{AEB} + 150^{\circ} - 20^{\circ} = 180^{\circ}$.
  • Simplify: $\angle\text{AEB} + 130^{\circ} = 180^{\circ}$.
  • Solve for $\angle\text{AEB}$: $\angle\text{AEB} = 180^{\circ} - 130^{\circ} = 50^{\circ}$.

Thus, the measure of angle AEB is $50^{\circ}$.

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Similar Questions

  1. In $\triangle ABC$, $BD \perp AC$ at $D$ and $\angle DBC = 40^\circ$. $E$ is a point on $BC$ such that $\angle CAE = 37^\circ$. What is the measure of $\angle AEB$?
  2. In $\Delta ABC$, $BD \perp AC$ at D and $\angle DBC = 71^\circ$. E is a point on BC such that $\angle CAE = 17^\circ$. What is the measure of $\angle AEB$?
  3. In triangle ABC, bisector of $\angle\text{ABC}$ and $\angle\text{ACB}$ meet at O. If $\angle\text{BAC} = 60^\circ$, then find the measure of $\angle\text{BOC}$.
  4. In $\Delta\text{XYZ}$, $\text{XY} = 12\text{ cm}$ and $\text{YZ} = 18\text{ cm}$. $\text{XW}$, the angle bisector of $\text{YXZ}$, meets $\text{YZ}$ at $\text{W}$, such that $\text{YW} : \text{WZ}$ is $4 : 5$. Find the length of the third side of the triangle.
  5. In $\Delta\text{PQR}$, $\text{QR}$ is extended up to $\text{S}$ so that $\text{RS} = \text{RP}$. If $\angle\text{PRQ} = 70^\circ$ and $\angle\text{QPS} = 110^\circ$ then find the measure of $\angle\text{PQS}$.
  6. The areas of two similar triangles are respectively $16\text{ m}^{2}$ and $36\text{ m}^{2}$. Find the ratio of their corresponding sides.
  7. In $\Delta PQR$, QR is extended up to S, so that RS = RP. If $\angle RPQ = 55^\circ$ and $\angle PRS = 110^\circ$, then find the measure of $\angle PQS$.
  8. The sides of a triangle are 44 cm, 33 cm, and 55 cm. What is its area? (in $cm^2$)
  9. The perimeter of an equilateral triangle ABC is 22.2 cm. What is the area of triangle (in $cm^2$)?
  10. In a triangle, if angle $A = 30^\circ$ and angle $B = 45^\circ$, then what is the angle of C?

Important Questions from Triangles

  1. What is the foot of the altitude from the vertex A of the triangle ABC?

  2. In ΔABC, D is a point on BC such that ∠ADB = 2∠DAC, ∠BAC = 70° and ∠B = 56°. What is the measure of ∠ADC?

  3. In ΔABC, ∠A = 66° and ∠B = 50 °. If the bisectors of ∠B and ∠C meet at P, then ∠BPC – ∠PCA = ?

  4. In a triangle ABC, points P and Q are on AB and AC, respectively, such that AP = 4 cm, PB = 6 cm, AQ = 5 cm and QC = 7.5 cm. If PQ = 6 cm, then find BC (in cm).

  5. The perimeters of two similar ΔABC and  Δ PQR are 48.4 cm and 12.1 cm, respectively. What is the ratio of the areas of  Δ ABC and  Δ PQR?

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