👉 Learn how to evaluate the secant of the sum or difference of two angles using the sum/difference formulas. To do this, we first use the Pythagoras theorem to obtain all the sides of the right ...

👉 Learn how to prove that two triangles are congruent. Two or more triangles are said to be congruent if they have the same shape and size. There are many postulates and theorems to determine whether ...

Prove two triangles are congruent by showing they satisfy one of four criteria. Find missing lengths by using the scale factor. The relationship between similar shapes may be expressed as a ratio.