ΔABD is a right-angled triangle.
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ΔABD is a right-angled triangle.
If we look at triangle ABD, we can see that we are given two angles: 90° and 17°.
Since the sum of all angles in a triangle equals 180°, we can calculate angle BAD as follows:
Since we know angle BAC, we can calculate angle CAD as follows:
12°
a is parallel to b.
Which of the angles in the drawing are adjacent to each other?
Those angles aren't directly related! The 61° is part of a larger angle, and 17° is at a completely different vertex. You need to find the whole angle ∠BAD first.
Look for a complete triangle! In triangle ABD, you have the right angle (90°), the 17° angle, and one unknown angle. These three must sum to 180°.
Always examine the diagram carefully! When you see a line like AC inside triangle ABD, it divides angle A into smaller angles. The 61° is just one piece of the larger angle.
No! The triangle angle sum (180°) is essential here. It's the only way to find the complete angle ∠BAD, which you need to subtract 61° from.
Follow the steps: Triangle ABD has angles that sum to 180°, so ∠BAD = 180° - 90° - 17° = 73°. Since ∠BAC = 61°, then ∠CAD = 73° - 61° = 12°.
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