JEE Exam  >  JEE Questions  >  How do I prove that sinA/2 + sinB/2 + sinC/2 ... Start Learning for Free
How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)?
Verified Answer
How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-...
This question is part of UPSC exam. View all JEE courses
Most Upvoted Answer
How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-...
Proof:

To prove the equation sin(A/2) * sin(B/2) * sin(C/2) = 1/4 * sin(π - A/4) * sin(π - B/4) * sin(π - C/4), we will use the trigonometric identities and properties of sine function.

Identity 1: sin(π - x) = sin(x)
Identity 2: sin(2θ) = 2sin(θ)cos(θ)
Property 1: sin(θ) = 2sin(θ/2)cos(θ/2)

Proof:

Step 1: Start with the left-hand side (LHS) of the equation:
LHS = sin(A/2) * sin(B/2) * sin(C/2)

Step 2: Apply Property 1 to each term:
LHS = 2sin(A/4)cos(A/4) * 2sin(B/4)cos(B/4) * 2sin(C/4)cos(C/4)

Step 3: Rearrange the terms:
LHS = (2sin(A/4) * 2sin(B/4) * 2sin(C/4)) * (cos(A/4) * cos(B/4) * cos(C/4))

Step 4: Simplify the product of the sines using Identity 2:
LHS = 8sin(A/4)sin(B/4)sin(C/4) * (cos(A/4) * cos(B/4) * cos(C/4))

Step 5: Use Identity 1 to rewrite cos(π - x) as cos(x):
LHS = 8sin(A/4)sin(B/4)sin(C/4) * (cos(π - A/4) * cos(π - B/4) * cos(π - C/4))

Step 6: Apply Property 1 to each term:
LHS = 8sin(A/4)sin(B/4)sin(C/4) * (2cos(A/8)sin(A/8) * 2cos(B/8)sin(B/8) * 2cos(C/8)sin(C/8))

Step 7: Rearrange the terms:
LHS = (8sin(A/4)sin(B/4)sin(C/4) * 2cos(A/8) * 2cos(B/8) * 2cos(C/8)) * (sin(A/8) * sin(B/8) * sin(C/8))

Step 8: Simplify the product of the cosines:
LHS = (8sin(A/4)sin(B/4)sin(C/4) * cos(A/8) * cos(B/8) * cos(C/8)) * (sin(A/8) * sin(B/8) * sin(C/8))

Step 9: Simplify the product of the sines:
LHS = 1/4 * sin(A/8) * sin(B/8) * sin(C/8) * (sin(A/8) * sin(B/8) * sin(C/8))

Step 10: Use Identity 2 to rewrite sin(2
Explore Courses for JEE exam
How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)?
Question Description
How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)?.
Solutions for How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)? in English & in Hindi are available as part of our courses for JEE. Download more important topics, notes, lectures and mock test series for JEE Exam by signing up for free.
Here you can find the meaning of How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)? defined & explained in the simplest way possible. Besides giving the explanation of How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)?, a detailed solution for How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)? has been provided alongside types of How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)? theory, EduRev gives you an ample number of questions to practice How do I prove that sinA/2 + sinB/2 + sinC/2 = 1+4 sin (π-A/4) sin (π-B/4) sin (π-C/4)? tests, examples and also practice JEE tests.
Explore Courses for JEE exam

Top Courses for JEE

Explore Courses
Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev