​how to find area of a triangle?

There are two formulas I know of. Multiply the base and the height together, then divide by 2, or take the two sides that create an angle, multiply them and then multiply them by the sine of the angle they create.

I'm a bit rusty though so I'd recommenf checking the second one.

I took a trignometry class at Portland Community College in Portland, Oregon last year in September and my math book says that the genral formula for the area of a triangle is \(K=\frac{1}{2}bh\) where \(K=area;\) \(b=base;\) \(h=height\).  If you know the lengths of two sides and an angle but do not know the base or the height, you can use the formula \(K=\frac{1}{2}ab\times sin(C)\)where \(K=area;\) a = side a; b = side b; C = angle C.  You can also use the formula\(K=\frac{1}{2}bc\times sin(A)\)where \(K=area;\) b = side b; c = side c; A = angle A.  You can also use the formula \(K=\frac{1}{2}ac\times sin(B)\)where \(K=area;\) a = side a; c = side c; B = angle B.  If you know the lengths of all three sides but do not know any of the angles, the base or the height, you can use the formula \(K=\sqrt{s\times(s-a)\times(s-b)\times(s-c)}\)where \(s=\frac{1}{2}\times(a+b+c);\)a = side a; b = side b; c = side c.