Question

Find, correct to five decimal places, the length of the side labeled x. a = 25 cm, b = 3π 8 rad

Answer 1

I am assuming from What I have found is that a is the base , b is angle between a and x and x is the hypotenuse . 
So we know that 
cos θ =base/hypotenuse 
here θ = 3Ď€/8 =67.5 degree 
cos 67.5 =0.38268 
so  
0.38268=a/x 
x=25/0.38268 
x=65.32873