Tan is equal to sin over cosine so if this is all the info you are given sin.is 3 and cosine is 4. However it is possible term cancel out like sin could be 3/5 and cosine 4/5 which would still give tan 3/4. Actually that is probably what it is to make a 3 4 5 triangle. To make sine and cos equal the opposite and adjacent sides must be equal. By corresponding angles it is isosceles so b and c must be 45