If a triangle ABCis not a right angled traingle abd inscribed in a fixed circle.If A,B,C be slightly varied then, `(d a)/(c a sA)+(d b)/(cosB)=0.`

Explanation

Given that side c and angle C are constant

so,`c/sinC=K`

`a/(sinA)=b/(sinB)=K`

`a=KsinA and b=KsinB`

`((da)/(dA))=KcosA and ((db)/(dB))=KcosB`

=`(da)/(cosA)+(db)/(cosB)=K(dA+dB).........(1) `


Also for the triangle ABC, `A+B+C=pi`

...