### Perpendicular Planes

Two planes lie perpendicular to one another. A line perpendicular to plane 1 and a line perpendicular…

### Line Perpendicular to Plane

If a straight line is perpendicular to each of two other straight lines in a plane at their point of…

### Line Perpendicular to Plane

Straight line AB is perpendicular to the lines in plane MN at point B.

### Line Perpendicular to Plane

Straight line AB is perpendicular to the lines in plane MN at point B. "If from the foot of a perpendicular…

### Lines Perpendicular to Plane

Two straight lines, AB and CD, perpendicular to the same plane (MN) are parallel.

### Sphere Tangent to Plane

Diagram used to prove the theorem: "A plane perpendicular to a radius at its extremity is tangent to…

### 3 Intersecting Planes

Illustration of three intersecting planes. "The intersections of two parallel planes by a third plane…

### 3 Intersecting Planes

Illustration of three intersecting planes. "The straight line perpendicular to one of two parallel lanes…

### Angles In Parallel Planes

"If two angles not in the same plane have their sides respectively parallel and lying in the same direction,…

### Intersecting Planes

Two intersecting planes on a third plane. "If two intersecting planes are each perpendicular to a third…

### Parallel Planes

"If two intersecting lines are each parallel to a given plane, the plane of these lines is parallel…

### Projection of a Line Segment

CD is the projection of AB upon OX. In each case AE=CD and AE=ABcos theta.

### Angles With Perpendicular Sides Are Equal or Supplementary Proof

Illustration used to prove "Two angles whose sides are perpendicular each to each are either equal or…

### Rectangle

Illustration of a rectangle, which is a parallelogram with all angles right angles.

### Refraction, air, water, glass

"Let a represent a, b water, and c a piece of glass. The ray d, striking each medium in a perpendicular…

### Refraction, glass and water

"Let the medium b be glass, and the medium c, water. The ray a, as it falls upon the medium b, is refracted…

### Sable Shield

A heraldic shield with a black surface, which is shown by the crossing horizontal and vertical lines.

### Lateral Sliding Contact

The lines of contact are equal, but the axes are neither parallel to each other, or the line of contact.

### Square

Illustration of a square, a rectangle with all sides equal.

### Perpendicular Between 2 Straight Lines

Diagram used to prove the theorem: "Between two straight lines not in the same plane only one perpendicular…

### Supplementary Angles 90 - 90

Supplementary Angles degrees 90 and 90

### Point of Tangency

Illustration of radius drawn to point of contact of a tangent.

### Tangent To A Circle

Draftsman's method to draw a tangent, AB, to a circle

### Tangent To Two Circles

Draftsman's method to draw a line tangent to two given circles

### Leaning Tower

Illustration of a leaning tower with a perpendicular drawn from the top of the tower to the ground to…

### Palm Tree Perpendicular to Ground

Illustration of a palm tree that is perpendicular to the ground. The tree is perfectly straight, as…

### Triangle ABC With Height h

Triangle ABC with sides a,b,c labeled and angles A,B,C labeled and h labeled as height.

### Triangle Accuracy Test using T-square

A test to ensure the triangle is accurate by drawing a perpendicular line from a T-square.

### Altitudes In A Triangle

Illustration used to show "The altitudes of a triangle are concurrent."

### Angle Bisectors In A Triangle

Illustration used to prove "The bisectors of the angles of a triangle are concurrent in a point which…

### Triangle With Bisector and Perpendicular From Vertex Drawn

Illustration to show the bisector of the vertical angle of a triangle makes with the perpendicular from…

### Obtuse Triangle ABC With Height h

Triangle ABC with sides a,b,c labeled and angles A,B,C labeled and h labeled as height.

### Perpendicular Bisector of the Base of an Isosceles Triangle

Illustration to show that the perpendicular bisector of the base of an isosceles triangle passes through…

### Perpendicular Bisectors In A Triangle

Illustration used to prove "The perpendicular bisectors of the sides of a triangle are concurrent in…

### Perpendiculars Dropped Any Point in the Equilateral Triangle

Illustration to show the perpendiculars dropped from any point in the equilateral triangle to the three…

### Perpendiculars Dropped From Midpoint of Base to Legs of Isosceles Triangles

Illustration to show the perpendiculars dropped from the midpoint of the base to the legs of an isosceles…

### Right Triangle

Illustration showing a right triangle (one that has one right angle).

### Right Triangle OCB With, x, y, and r shown

Right triangle OCB that can be used to show the relationships between x, y, r, and Θ.