In your case
The statement means that for all angles between 0 and 180 sin will be positive. Therefore the result you are after must be positive as we are taking that postive result and multiplying it by only positive numbers.
How can't you split into right angled triangles??
First use cosine rule to work out the length of the remaining side = 17.94cm
Then use sine rule and basic calculation (180-angle = other angle) to work out
BCA = 25.39
CAB = 48.61
Then use use trig functions (sine and cosine) to work out length and height of triangles
And calculate the triangle with 1/2 base times height.
A = 53.8cm2