If a ladder makes an angle of 45° with the wall and the ladder is 5 m away from the wall, what is the height of the wall (the ladder’s top)?

Correct answer: 5 m. tan 45° = 1 = 5 ÷ height, so height = 5 m.

Background: At 45°, the triangle is isosceles, so base = height.

• 10 m: 10 m does not match tan 45° = 1.
• 15 m: 15 m does not match tan 45° = 1.
• 45√3 m: 45√3 m does not match tan 45° = 1.

Did you know? tan 45° = 1.

Memory trick: 45° → equal sides.