6 Questions around this concept.
In Triangle ABC, point D is on BC is such that $A D \perp B C$ and E is the middle point of BC and $b^2+2 a^2=c^2$ distance between D and E is?
Projection Formula
In the $\triangle A B C$,
The projection of $A B$ on $B C$ is $B D$ and the Projection of $A C$ on $B C$ is $D C$

Now,
$
\begin{aligned}
& B D=c \cos B \text { and } D C=b \cos C \\
& \text { and, } B C=a=B D+D C \\
& =c \cos B+b \cos C \\
& a=c \cos B+b \cos C
\end{aligned}
$
Similarly, other projection formulas can be derived
$
\begin{aligned}
& a=c \cos B+b \cos C \\
& b=c \cos A+a \cos C \\
& c=b \cos A+a \cos B
\end{aligned}
$
"Stay in the loop. Receive exam news, study resources, and expert advice!"
Mathematics for Joint Entrance Examination JEE (Advanced) : Trigonometry
Page No. : 5.9
Line : 21
8105+ Downloads
6680+ Downloads
7777+ Downloads
4642+ Downloads
Among top 100 Universities Globally in the Times Higher Education (THE) Interdisciplinary Science Rankings 2026
Application Deadline: 15th April | Recognized as Institute of Eminence by Govt. of India | NAAC ‘A++’ Grade | Upto 75% Scholarships
Mark presence in the Modern Architectural field with Bachelor of Architecture | Highest CTC : 70 LPA | Accepts NATA Score
Integrated M.Tech admissions open @ VIT Bhopal University | Highest CTC 70 LPA | Application Closing Soon | Apply now
Final Application Deadline: 23rd March | NAAC A++ Accredited | Accorded institution of Eminence by Govt. of India | NIRF Rank #3
Top Recruiters: Qatar Airways, Air Asia, SpiceJet, Flydocs etc.
Explore on Careers360
Student Community: Where Questions Find Answers