Q. An isosceles triangle has congruent sides of 20cm. The base is 10cm. What is the area of the triangle?A=81cm2a=9
Identify Triangle Area Formula: To find the area of the triangle, we need to use the formula for the area of a triangle, which is A=21×base×height. We know the base is 10cm, but we need to find the height.
Use Pythagorean Theorem: Since the triangle is isosceles, the height will create two right-angled triangles when drawn from the vertex opposite the base to the midpoint of the base. We can use the Pythagorean theorem to find the height h.
Apply Pythagorean Theorem: The Pythagorean theorem states that in a right-angled triangle, the square of the length of the hypotenuse c is equal to the sum of the squares of the lengths of the other two sides a and b. In our case, the hypotenuse is one of the congruent sides of the triangle, which is 20 cm, and one of the other sides is half of the base, which is 5 cm (since the height bisects the base). So we have c=20 cm and a=5 cm. We need to find b, which is the height h.
Calculate Height: Using the Pythagorean theorem, we have: c2=a2+b2, which becomes 202=52+h2. This simplifies to 400=25+h2.
Find Area Formula: Subtracting 25 from both sides to solve for h2 gives us h2=400−25, which simplifies to h2=375.
Calculate Area: Taking the square root of both sides to solve for h gives us h=375. Calculating the square root of 375 gives us h≈19.36 cm.
Calculate Area: Taking the square root of both sides to solve for h gives us h=375. Calculating the square root of 375 gives us h≈19.36 cm.Now that we have the height, we can find the area of the triangle using the formula A=21×base×height. Plugging in the values, we get A=21×10cm×19.36cm.
Calculate Area: Taking the square root of both sides to solve for h gives us h=375. Calculating the square root of 375 gives us h≈19.36 cm. Now that we have the height, we can find the area of the triangle using the formula A=21×base×height. Plugging in the values, we get A=21×10 cm ×19.36 cm. Calculating the area gives us A=5 cm ×19.36 cm, which equals 96.8 cmh=3750.