Questions: Example 2: Missing Data: Lengths of Two Sides
Transcript text: Example 2: Missing Data: Lengths of Two Sides
Solution
Solution Steps
Step 1: Analyze the given information
We are given a quadrilateral ABCD. We know the length of AB = 610.67 and the measures of the following angles:
∠DAB = 83°46'
∠ABC = 92°38'
∠CDA = 46°21'
∠ADB = 70°8.01', so ∠ADC = 70°8.01' + 46°21' = 116°29.01'
We also know the length of AD = 512.57 and the length of CD = 462.1
We are looking for the lengths of BC and CD. We are given the length of CD so we are looking for BC.
Step 2: Solve for the length of BC
We are given CD.
Since we know two sides (AD and AB) and the angle between them (∠DAB), we can solve for the length of BD using the law of cosines. For triangle ABD:
BD² = AD² + AB² - 2 * AD * AB * cos(∠DAB)
BD² = 512.57² + 610.67² - 2 * 512.57 * 610.67 * cos(83°46')
BD² = 262716.3049 + 372926.9489 - 625452.7938 * cos(83.7667°)
BD² ≈ 262716.30 + 372926.95 - 625452.79 * 0.1111
BD² ≈ 635643.25 - 69478.55
BD² ≈ 566164.7
BD ≈ 752.44
Now, in triangle BCD we know the lengths of BD and CD and the angle between them, so we can use the law of cosines again: