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Eamcet Mathematics
Trigonometry Properties of Triangles

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If a²,b²,c² are in A. P. then which of the following are also in A.P.

A. sinA,sinB,sinC

B. tanA,tanB,tanC

C. cotA,cotB,cotC

D. cosA,cosB,cosC

E. None of the above

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Correct choice: C

Explanation:

sin²B - sin²A=sin²C -sin²B
∴sin(B+A)sin(B-A)= sin(C+B)sin(C-B)
or sinC(sinBcosA - cosB sinA)
= sin A(sinC cos B - cos C sinB)
Divide by sinAsinBsinC
∴cotA - cotB = cotB - cot C

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Eamcet Mathematics Trigonometry Properties of Triangles

Eamcet Mathematics
Trigonometry Properties of Triangles