Home
Class 11
MATHS
Prove that : sin 51^0+cos 81^0=cos 21^0...

Prove that `: sin 51^0+cos 81^0=cos 21^0`

Text Solution

Verified by Experts

We have to proof,
`sin(51^o)+cos(81^o)=cos(21^o)`
Let,
L.H.S.=`sin(51^o)+cos(81^o)`
L.H.S=`sin(51^o)+cos((90^o)-(9^o))`
L.H.S=`sin(51^o)-sin(9^o)`
As we know the formula,
`sin(A^o)+sin(B^o)= 2[sin(((A^o) +(B^o))/2)cos(((A^o)-(B^o))/2)]`
then, ...
Promotional Banner

Topper's Solved these Questions

  • THE STRAIGHT LINES

    RD SHARMA|Exercise Solved Examples And Exercises|488 Videos

  • TRIGONOMETRIC EQUATIONS

    RD SHARMA|Exercise Solved Examples And Exercises|120 Videos

Similar Questions

Explore conceptually related problems

Prove that: "sin"51^(@)+cos81^(@)=cos21^(@) .

"sin" 51^(@)+cos 81^(@)=cos 21^(@) .

Prove that: 4cos12^(0)cos48^(0)cos72^(0)=cos36^(@)

Prove that cos65^(@)+cos115^(0)=0

Prove that: cos7^(0)cos14^(0)cos28^(0)cos56^(@)=(s in68^(0))/(16cos83^(@))

Prove that: cos55^(@)+cos65^(0)+cos175^(0)=0

Prove that: sin65^(@)+cos65^(0)=sqrt(2)cos20^(@)

Prove that: (cos11^(0)+sin11^(0))/(cos11^(0)-sin11^(0))=tan56^(@)

Prove that: sin6^(@)cos42^(0)cos60^(@)quad in78^(0)=(1)/(16)