Solve the following tasks from sequences.
Three consecutive terms of an increasing geometric sequence have a sum of 52. If we add 1 to the first term, 8 to the second, and subtract 1 from the third, we get consecutive terms of an arithmetic sequence. Calculate the first three terms of both sequences.
The interior angles of the triangle 
, 
and 
are successive terms of an arithmetic sequence. Prove that the sides a, b and c of this triangle have the relation 
.
Calculate all values of the parameter m, 
so that the solutions of the equation 
consecutive terms of an arithmetic sequence.
is calculated, then the cosine theorem is applied to the side b.
