Question

Find the missing lengths in the triangle above
ER=
IE=

Answer 1

Explanation:

IR = 9√3

E = 60°

I = 30°

R = 90°

• Find ER.

ER/sin(I) = IR/sin(E)

ER/sin(30°) = 9√3/sin(60°)

ER/(1/2) = 9√3/(1/2 √3)

ER/(1/2) = (9√3 . 2)/√3

ER/(1/2) = 18√3/√3

ER/(1/2) = 18 → IR/sin(E)

ER = 18 . 1/2

ER = 9 is the answer

• Find IE (There are 2 ways).

First, using a Sinus Rule.

IE/sin(R) = IR/sin(E)

IE/sin(90°) = 9√3/sin(60°)

IE/1 = 9√3/(1/2 √3)

IE = (9√3 . 2)/√3

IE = (18√3)/√3

IE = 18 is the answer

Second, using a Pythagoras Theorem.

IE = √(IR² + ER²)

IE = √((9√3)² + 9²)

IE = √(81.3 + 81)

IE = √(243 + 81)

IE = √324

IE = 18 is the answer