Question 1077090
sum of other remaining angles = 180-45 = 135 deg
Hence, each angle = 135/2 = 67.5 deg
Hence, base = 2.5cos67.5+2.5cos67.5 
= 2*2.5cos67.5
= 1.9134meters
we can use cosine rule also.
cos45=(2.5^2+2.5^2-base^2)/(2*2.5*2.5)
solving it, we get base = 1.9134meters.