Grades 7-8 Video Solutions 2026-2026_7-8

Video Transcription

Video Summary

The triangle is rotated about point B, so corresponding angles and side lengths are preserved. Since ∠BCA = 15°, the matching angle in the rotated triangle is also 15°. Also, BC = BC', so triangle BCC' is isosceles, making its base angles equal. Thus ∠BCC' = 15°, and the angle at C in triangle ACC' is 30°. In triangle ACC', the angles are 30° at C and 15° at C', so ∠A = 180° − 30° − 15° = 135°. Therefore, ∠BAC = 135°.

Keywords

triangle rotation

corresponding angles

isosceles triangle

angle preservation

geometry proof