also prove that

arccosx = 2arccos sqrt ( (x+1)/2 )

for the first one i let the LHS be y but didnt know where to go next

for the second one i cosined both sides but am still unsure

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- March 25th 2009, 02:23 AMb0mb3rzshow that arctanx = arcsin(x/sqrt (1+x^2)
also prove that

arccosx = 2arccos sqrt ( (x+1)/2 )

for the first one i let the LHS be y but didnt know where to go next

for the second one i cosined both sides but am still unsure - March 25th 2009, 03:03 AMPlato
- March 25th 2009, 08:10 AMSoroban
Hello, b0mb3rz!

Quote:

Prove that: .

The right side is: .

Take the cosine of both sides:

. . .[2]

Substitute [1] into [2]: .

We have: .

. . Then: .

Therefore: .