If in a triangle ,tanA.tanB=2,Then find the value of cosA.cosB/cosC
If in a triangle ,tanA.tanB=2,
Then find the value of cosA.cosB/cosC
Vedit , 8 Years ago
Grade 11
Trigonometry> If in a triangle ,tanA.tanB=2, Then find ...
1 Answers
Arun
you can write-
sinA sinB= 2 cosA cosB
now sinA sinB –cosA cosB= cosA cosB
thus cos (A+B)= cosA cosB
now in a triangle, A+B= 
–C
thus cos(–C) = cosA cosB
so cosA*cosB/cosC= – 1
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