1 Answer

Gert Kommer · Answer 1 · 2023-07-31T05:43:33+0000

Answer:

m∠ABC = 67.5°

Explanation:

ABC is an isosceles triangle

Then

m∠ABC = m∠ACB

The sum of the interior angles of a triangle is equal to 180°

Then

m∠ABC + m∠ACB + m∠BAC = 180°

Then

m∠ABC + m∠ACB + 45 = 180°

Then

2 × m∠ABC = 180°

Then

m∠ABC = (180−45)÷ 2 = 67.5°

Law of SIN :

$(9)/(\sin \left( 67.5\right) ) =(BC)/(\sin \left( 45\right) )$

$BC=(9)/(\sin \left( 67.5\right) ) * \sin \left( 45\right) ==6.888301782572$