The base is the easy part: just use the third, unequal side of the isosceles. For example, if your isosceles triangle has sides of 5 centimeters, 5 cm, and 6 cm, use 6 cm as the base. read more
To find the area of an isosceles triangle, multiply the base, or width at the bottom of the triangle, and the height at tits tallest point, then divide the product in half. The base is the bottom side, or the side that is not equal to the other two. read more