Question

Please solve number 15 for me friends.... 50 marks qn... please help me.... ♥ ​

Answer 1

HEY ISHU. HERE IS YOUR ANSWER ⭐

As A, B, C, D are the vertices of Quadrilater ABCD,

A+C=180° and B+D=180°

By the rules of *associated angles*, we can write,

CosC=Cos(2x90-A)= -CosA.....(1)

We can apply the same process on CosB or CosD......

Then we shall get,

CosB=-CosD................................ (2)

So, in L. H. S.

CosA+CosB+CosC+CosD

=CosA-CosD-CosA+CosD........ From 1&2

=0

Hence, L.H.S=R.H.S., |PROVED|

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Answer 2

Answer:

HEYA MATE HERE'S YOUR REQUIRED PROOF:-HOPE THIS HELPS..☺️