The problem asks us to find the values of $x$ and $y$ in two right triangles using trigonometric ratios. In the first triangle, the hypotenuse is 12cm, and one angle is 45 degrees. We need to find $x$ (opposite) and $y$ (adjacent). In the second triangle, the hypotenuse is 6km, one angle is 30 degrees, and we need to find $x$ (opposite) and $y$ (adjacent). Then, we're asked to use the values found to calculate another value of $y$ given $x = 3km$ and an angle of $30^\circ$.

GeometryTrigonometryRight TrianglesSineCosineTangentAngle Relationships
2025/3/11

1. Problem Description

The problem asks us to find the values of xx and yy in two right triangles using trigonometric ratios. In the first triangle, the hypotenuse is 12cm, and one angle is 45 degrees. We need to find xx (opposite) and yy (adjacent). In the second triangle, the hypotenuse is 6km, one angle is 30 degrees, and we need to find xx (opposite) and yy (adjacent). Then, we're asked to use the values found to calculate another value of yy given x=3kmx = 3km and an angle of 3030^\circ.

2. Solution Steps

For the first triangle:
(i) To find yy (adjacent), we can use the cosine function:
cos(θ)=adjacenthypotenusecos(\theta) = \frac{adjacent}{hypotenuse}
cos(45)=y12cos(45^\circ) = \frac{y}{12}
y=12cos(45)y = 12 \cdot cos(45^\circ)
y=1222=62y = 12 \cdot \frac{\sqrt{2}}{2} = 6\sqrt{2}
y8.485cmy \approx 8.485 cm
(ii) To find xx (opposite), we can use the sine function:
sin(θ)=oppositehypotenusesin(\theta) = \frac{opposite}{hypotenuse}
sin(45)=x12sin(45^\circ) = \frac{x}{12}
x=12sin(45)x = 12 \cdot sin(45^\circ)
x=1222=62x = 12 \cdot \frac{\sqrt{2}}{2} = 6\sqrt{2}
x8.485cmx \approx 8.485 cm
For the second triangle:
(i) To find xx (opposite), we can use the sine function:
sin(θ)=oppositehypotenusesin(\theta) = \frac{opposite}{hypotenuse}
sin(30)=x6sin(30^\circ) = \frac{x}{6}
x=6sin(30)x = 6 \cdot sin(30^\circ)
x=612=3kmx = 6 \cdot \frac{1}{2} = 3 km
(ii) The final part involves using the tangent function and the previously calculated value of x=3kmx=3km and the given angle of 3030^\circ to find yy:
tan(θ)=oppositeadjacenttan(\theta) = \frac{opposite}{adjacent}
tan(30)=3ytan(30^\circ) = \frac{3}{y}
y=3tan(30)y = \frac{3}{tan(30^\circ)}
y=313=33y = \frac{3}{\frac{1}{\sqrt{3}}} = 3\sqrt{3}
y5.196kmy \approx 5.196 km

3. Final Answer

y8.485cmy \approx 8.485 cm
x8.485cmx \approx 8.485 cm
x=3kmx = 3 km
y5.196kmy \approx 5.196 km

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