Confusing parallel with collinear H

"The Parallel Pitfall"

Geometry & Shapes

Ignoring direction (negative signs)

"The One-Way Street"

Geometry & Shapes

Writing column vectors as fractions

"The Fraction Habit"

Geometry & Shapes

Confusing "bearing of A from B" with "bearing of B from A"

"The From Confusion"

Geometry & Shapes

Confusing opposite and adjacent sides

"The O-A Swap"

Geometry & Shapes

Finding $c^2$ instead of $c$

"The Forgotten Root"

Geometry & Shapes

Forgetting to include radii in sector perimeter

"The Missing Radii"

Geometry & Shapes

Halving instead of doubling for angle at centre H

"The Half-Double Confusion"

Geometry & Shapes

Incomplete transformation description

"The Missing Detail"

Geometry & Shapes

Using 180° as the sum for all polygons

"The Triangle Default"

Geometry & Shapes

Using diameter instead of radius in circle formulas

"The D-R Disaster"

Geometry & Shapes

Using length scale factor for area

"The Area Scale Slip"

Geometry & Shapes

Using the wrong trigonometric rule H

"The Rule Mix-Up"

Geometry & Shapes

Adding adjacent instead of opposite angles in cyclic quadrilateral H

"The Adjacent Angle Error"

Geometry & Shapes

Adding when finding a shorter side

"The Plus-Minus Mixup"

Geometry & Shapes

Calculator set to radians instead of degrees

"The Mode Mishap"

Geometry & Shapes

Confusing interior and exterior angle formulas

"The Inside-Out Error"

Geometry & Shapes

Getting the angle fraction upside down

"The Fraction Flip"

Geometry & Shapes

Matching wrong corresponding sides

"The Side Mismatch"

Geometry & Shapes

Measuring anticlockwise instead of clockwise

"The Wrong Direction"

Geometry & Shapes

Sign error in the cosine rule H

"The Sign Slip"

Geometry & Shapes

Using slant height instead of perpendicular height

"The Slant Slip"

Geometry & Shapes

Wrong signs in translation vectors

"The Vector Sign Slip"

Geometry & Shapes

Enlarging from wrong point

"The Centre Confusion"

Geometry & Shapes

Forgetting tangent-radius is 90° H

"The Right Angle Oversight"

Geometry & Shapes

Forgetting the ½ in triangle area

"The Missing Half"

Geometry & Shapes

Labelling the wrong side as the hypotenuse

"The Hypotenuse Hijack"

Geometry & Shapes

Mixing up alternate and co-interior angles

"The Z and C Confusion"

Geometry & Shapes

Not using inverse functions to find angles

"The Inverse Forget"

Geometry & Shapes

Not using three figures for bearings

"The Missing Zero"

Geometry & Shapes

Thinking AAA proves congruence

"The AAA Assumption"

Geometry & Shapes

Using diameter instead of radius in arc/sector formulas

"The D for R Disaster"

Geometry & Shapes

Using the wrong angle in the area formula H

"The Wrong Angle"

Geometry & Shapes

Confusing clockwise and anticlockwise

"The Direction Dilemma"

Geometry & Shapes

Ignoring the ambiguous case H

"The Missing Answer"

Geometry & Shapes

Mixing up exact trig values for 30° and 60° H

"The 30-60 Swap"

Geometry & Shapes

Using degree formula with radians or vice versa H

"The Radian Wrangle"

Geometry & Shapes