Problem Solving : If 3 +2 = 7 , 5 +4 = 23 , 7 +6 = 47 and 9 +8 = 79 to what is 10 +9 equal ?
If theta is the angle between the diagonals of a parallelogram ABCD whose vertices are A -LRB- 0,2 -RRB- , B -LRB- 2,-1 -RRB- , C -LRB- 4,0 -RRB- and D -LRB- 2,3 -RRB- . show that tan theta = 2 ?