In $ riangle ABC$, $\angle BCA$ is obtuse and $CD$ is the orthogonal projection of $AC$ on the extended $BC$. Then —

Question

In $	riangle ABC$, $\angle BCA$ is obtuse and $CD$ is the orthogonal projection of $AC$ on the extended $BC$. Then —

Accepted Answer

$AB^2 = AC^2 + BC^2 + 2 BC \cdot CD$

Answer

$AB^2 = AC^2 + BC^2$

Answer

$AB^2 = AC^2 + BC^2 - 2 BC \cdot CD$

Answer

$AB^2 = AC^2 - BC^2$

In △ABC\triangle ABC△ABC, ∠BCA\angle BCA∠BCA is obtuse and CDCDCD is the orthogonal projection of ACACAC on the extended BCBCBC. Then —