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
Among top 100 Universities Globally in the Times Higher Education (THE) Interdisciplinary Science Rankings 2026
Recognized as Institute of Eminence by Govt. of India | NAAC ‘A++’ Grade | Upto 75% Scholarships | Application Deadline: 15th Jan
UG Admissions Open 2026 | Highest CTC 52 LPA | Average CTC 9.09 LPA | 60+ Collaborations with the world's best Universities
Highest CTC 44.14 LPA | UGC Approved | 1600+ Recruiters | 100% Placement
Institute of Eminence (IOE) by Govt. of India | Merit Based Scholarships | Ranked #11 by NIRF | Last Date to Apply: 16th Mar'26
Gateway to B.Tech, B.Tech + MBA Tech.,B.Pharma + MBA (Pharma Tech.) @ NMIMS (Deemed to be University)
Explore on Careers360
Student Community: Where Questions Find Answers