$\Delta ABC$ is an acute-angled triangle and $\overline{AM}$ is an altitude. Prove that $AC^{2} = AB^{2} + BC^{2} - 2 \cdot BC \cdot BM$.

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) In $\Delta ABC$,$\overline{AM}$ is the altitude to side $\overline{BC}$,so $\angle AMB = 90^{\circ}$ and $\angle AMC = 90^{\circ}$.
In $\Delta AMC$,by Pythagoras theorem: $AC^{2} = AM^{2} + MC^{2}$.
Since $M$ lies on $BC$,we have $MC = BC - BM$.
Substituting this into the equation: $AC^{2} = AM^{2} + (BC - BM)^{2}$.
Expanding the square: $AC^{2} = AM^{2} + BC^{2} + BM^{2} - 2 \cdot BC \cdot BM$.
In $\Delta AMB$,by Pythagoras theorem: $AB^{2} = AM^{2} + BM^{2}$.
Substituting $AM^{2} + BM^{2} = AB^{2}$ into the equation: $AC^{2} = AB^{2} + BC^{2} - 2 \cdot BC \cdot BM$.
Hence,the result is proved.

Explore More

Similar Questions

In $\Delta ABC$,$m \angle A + m \angle C = m \angle B$ and $AC : AB = 17 : 15$. If $BC = 8$,then the area of $\Delta ABC$ is.............

Difficult
View Solution

In the given figure,if $\angle 1 = \angle 2$ and $\triangle NSQ \cong \triangle MTR,$ then prove that $\triangle PTS \sim \triangle PRQ.$

Difficult
View Solution

In $\Delta ABC$,$\overline{AD}$ is a median and $AB^2 + AC^2 = 148$. If $AD = 7$,then $BC = \ldots$

In $\Delta PQR$,$m\angle Q = 90^{\circ}$,$PR = a^{2} + b^{2}$ and $QR = a^{2} - b^{2}$. Then,$PQ = \ldots$ $(a, b \in R^{+}; a > b)$

Difficult
View Solution

In $\Delta ABC$,$\overline{AB} \cong \overline{AC}$ and $\overline{AD}$ is a median. If $AD = 12$ and the perimeter of $\Delta ABC$ is $36$,find the area of $\Delta ABC$.

Difficult
View Solution

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo