if triangle abc ,cosA.cosB+sinA.sinC=1 show that a:b:c=1:1:√2
sumit suman , 9 Years ago
Grade 12th pass
1 Answers
Vikas TU
This ithe pure identity.
Take LHS and write them in other form that is:
cosA.cosB+sinA.sinC=1
cos(A+B) + cos(A-B) +cos(A-B) – cos(A+B) = 2
2cos(A-B) = 2
Cos(A-B) = 1
A-B = 0
A= B
Hence two angles are same the triangle is isscoeles. And therfore two sides opposite to that angle would be same too. Hence they both would share equal side ratio. And soothes the ratio 1:1:root(2)
Last Activity: 9 Years ago
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