Find the acute corners of a right-angled triangle with a hypotenuse of 32cm, knowing that its area is 128cm2.
Let’s denote the legs of this right-angled triangle through a and b.
Since the area of this triangle is 128 cm ^ 2, and the hypotenuse is 32 cm, the following relations take place:
a * b / 2 = 128;
a ^ 2 + b ^ 2 = 32 ^ 2.
We solve the resulting system of equations.
Multiplying both sides of the first equation by 4 and adding the resulting ratio with the second equation, we get:
a ^ 2 + b ^ 2 + 4 * (a * b / 2) = 32 ^ 2 + 4 * 128;
a ^ 2 + b ^ 2 + 2a * b = 1024 + 512;
(a + b) ^ 2 = 1536;
a + b = 16√6.
Multiplying both sides of the first equation by 4 and subtracting the resulting ratio from the second equation, we get:
a ^ 2 + b ^ 2 – 4 * (a * b / 2) = 32 ^ 2 – 4 * 128;
a ^ 2 + b ^ 2 – 2a * b = 1024 – 512;
(a – b) ^ 2 = 512;
a – b = 16√2.
Adding the ratios a + b = 16√6 and a – b = 16√2, we get:
a + b + a – b = 16√6 + 16√2;
2a = 16√6 + 16√2;
a = (16√6 + 16√2) / 2 = 8√6 + 8√2.
Find b:
b = 16√6 – a = 16√6 – (8√6 + 8√2) = 8√6 – 8√2.
We find the sine of the angle α, which lies opposite the leg a:
sin (α) = (8√6 + 8√2) / 32 = (√6 + √2) / 4.
We find the sine of the angle β, which lies opposite leg b:
sin (β) = (8√6 – 8√2) / 32 = (√6 – √2) / 4.
Therefore, α = arcsin ((√6 + √2) / 4) and β = arcsin ((√6 – √2) / 4).
Answer: arcsin ((√6 + √2) / 4) and arcsin ((√6 – √2) / 4).