Geometry
ACT geometry is mostly recognition. Match the figure to the right fact or formula, then solve only for the quantity asked.
核心知识
On ACT geometry, speed comes from recognition. Identify the figure, match it to the governing fact or formula, and solve only the quantity the question actually asks for.
深入理解
Rule: ACT geometry is mostly a recognition test, not a memorization dump. Similarity, congruence, area, volume, right-triangle ratios, angle rules, coordinate formulas, circle facts, and conic patterns all become manageable once you identify what stays fixed: equal angles, proportional sides, constant slope, or a standard equation form.
A reliable workflow is simple: sketch or label the figure, mark the key relationship, write the shortest useful formula, and check that your answer matches the requested quantity. Many misses come from solving for a side when the question asked for area, using diameter instead of radius, or matching the wrong corresponding parts.
知识点教程
8Use angle relationships (parallel lines, polygons) and triangle properties.
Most angle problems reduce to a few standard facts about lines, triangles, and polygons.
Apply similarity and congruence; use proportional reasoning in similar figures.
Similar figures use a constant scale factor, and congruent figures match side for side.
Solve right-triangle problems using trigonometric ratios; use special right triangles.
Use special right-triangle ratios first, then fall back on sine, cosine, or tangent.
Work with circles (arcs, chords, tangents, central/inscribed angles) and circle equations when presented.
Circle questions usually come down to arc, radius, or standard-form relationships.
Use coordinate geometry (distance, midpoint, slope; parallel/perpendicular lines).
Use slope, midpoint, and distance as the main coordinate-geometry tools.
Compute area and perimeter of plane figures, including composite figures.
Break composite figures into familiar pieces for area and trace only the outside edge for perimeter.
Compute volume and surface area of solids (prisms, cylinders, pyramids, cones, spheres).
Choose the solid and the measure first: inside space for volume, outer covering for surface area.
Work with conic sections (parabolas/ellipses/hyperbolas) and their equations when presented.
Conic questions are mainly pattern-recognition: identify the curve and read its standard form.