Trigonometry

[Marius]

1.
ABC triangle
Tan(A/2)=1/3
b+c=3a
Prove that B=pi/2 or C=pi/2

2.
ABC triangle
b, a , c arithmetic progression
2a=b+c
The value of the expression E=tan(B/2)*tan(C/2) is ?

I need some help

 

[Deleted member 4993]

1.
ABC triangle
Tan(A/2)=1/3
b+c=3a
Prove that B=pi/2 or C=pi/2

2.
ABC triangle
b, a , c arithmetic progression
2a=b+c
The value of the expression E=tan(B/2)*tan(C/2) is ?

I need some help

Do you know the laws of sines and cosines for plane triangles?

Please share your work with us.

You need to read the rules of this forum. Please read the post titled "Read before Posting" at the following URL:

http://www.freemathhelp.com/forum/th...217#post322217

We can help - we only help after you have shown your work - or ask a specific question (e.g. "are these correct?")

 

[Marius]

a/sinA=b/sinB=c/sinC=2R
a^2=b^2+c^2-2bc*cosA
How can i use them ?

 

[Deleted member 4993]

a/sinA=b/sinB=c/sinC=2R
a^2=b^2+c^2-2bc*cosA
How can i use them ?

For the first problem... you need to show Cos(A) = 4/5 and then b² = a² + c²

Show work...