Sine rule
a/Sin(A) = b/Sin(B) = c/Sin(C)
b
C / |
a / _| A
B c
We know that a = 70 degrees and A = 25 foot
So 70/Sin(25) = Something
We also know we want C, and that c = 90 degrees
So 70/Sin(25) = 90/Sin(C)
Then you have to rearrange the equations. Start with Multiply all by Sin(C)
So [Sin(C)][70/Sin(25)] = 90
Then divide everything by 70/Sin(25)
So Sin(C) = 90/[70/Sin(25)]
Now you want to isolate C, so Sin-1 everthing
So C = Sin-1{90/[70/Sin(25)]}
So C = 32.91309534
To the nearest tenth, 32.9ft
Hope that helps :)
