Create your Smart Home App in the Free Webinar on Home Automation. Register Now
One of our academic counsellors will contact you within 1 working day.
Click to Chat
1800-1023-196
+91-120-4616500
CART 0
Use Coupon: CART20 and get 20% off on all online Study Material
Welcome User
OR
LOGIN
Complete Your Registration (Step 2 of 2 )
Free webinar on App Development Learn to create your own Smart Home App
16th Jan @ 5:00PM for Grade 1 to 10
Sit and relax as our customer representative will contact you within 1 business day
if cos(b - c) + cos(c - a) + cos(a - b) = -3/2 , then show that cos a + cos b + cos c = 0 = sin a +sin b + sin c
cos(A−B)+cos(B−C)+cos(C−A)=−3/2 cosA⋅cosB+sinA⋅sinB+cosB⋅cosC+sinB⋅sinC+cosC⋅cosA+sinC⋅sinA=−3/22(cosa.cosb+sina.sinb+cosb.cosc+sinb.sinc+cosc.cosa+sinc.sina)+3=0.Now we write 3 as (cos^2 a+sin^2 a)+(cos^2 b+sin^2 b)+(cos^2 c+sin^2 c) and substitute this in. We then make use of the identity(x+y+z)^2=x^2+y^2+z^2+2(xy+yz+zx)to obtain that(cosa+cosb+cosc)2+(sina+sinb+sinc)2=0from which the claim follows easily.Here x^2means x square and similarly in others.
Post Question
Dear , Preparing for entrance exams? Register yourself for the free demo class from askiitians.
points won -