Question

if m∠acb = 180°, and m∠acd = 55°, then m∠dcb = ?°

Explanation:

Step1: Use the angle - addition property

Since \(\angle ACB\) is a straight angle (\(m\angle ACB = 180^{\circ}\)) and \(\angle ACB=\angle ACD+\angle DCB\).

Step2: Solve for \(\angle DCB\)

We know that \(m\angle ACD = 55^{\circ}\). Substitute into the equation \(m\angle DCB=m\angle ACB - m\angle ACD\). Then \(m\angle DCB=180^{\circ}- 55^{\circ}\).

Answer:

\(125\)