numero 144
utilizzando teorema area triangolo
area=1/2×lato×lato×seno angolo compreso
COS(α) = 12/13
SIN(α) = √(1 - (12/13)^2)-----> SIN(α) = 5/13
A=1/2·28·39·5/13 = 210 cm^2
COS(α) = 12/13
SIN(α) = √(1 - (12/13)^2)
SIN(α) = 5/13
A=(1/2)•28•39·•(5/13)= 210 cm^2