Start with a picture. Follow the argument. Look closely at the step where everything clicks.
Put four right triangles inside a square of side a+b. Each triangle has area ab/2.
Follow the argument →For x>0, a square of side x has area x².
Follow the argument →Divide the circle into an even number of congruent sectors. Cutting changes neither the area nor the curved boundary lengths.
Follow the argument →Let x change by h. The inner function multiplies this change by 3.
Follow the argument →Its side vectors are e₁ and e₂; its area is one.
Follow the argument →A complex number is a length paired with an angle. Zero has no unique angle.
Follow the argument →Fix a lower endpoint a and let the upper endpoint vary.
Follow the argument →Start with a finite expression so every subtraction is justified.
Follow the argument →At angle θ, define x=cos θ and y=sin θ on the unit circle.
Follow the argument →We seek a nonzero vector whose image is a scalar multiple of itself. A negative multiple reverses direction.
Follow the argument →Every sequence states its assumptions and scope. Some establish a complete identity, some prove a worked case, and others use a limit argument. The label tells you which. Use Prove inside a lesson to step backward, pause, or hide its equation.