Question

Given: △ABC, m∠A=60°, m∠C=45°, AB=9 Find: Perimeter of △ABC, Area of △ABC do not rationlize

Answer 1

Answer:

p = 32.32; A = 47.91  

Step-by-step explanation:

1. Calculate ∠B

∠A + ∠B + ∠C = 180°

60° + ∠B + 45° = 180°

       ∠B + 105° = 180°

                  ∠B =   75°

2. Find sides BC and AC

We can use the Law of Sines

$\dfrac{\sin A}{BC} = \dfrac{\sin B}{AC} = \dfrac{\sin C}{AB}$

(i) Find BC

$\dfrac{\sin 75^{\circ}}{AC} = \dfrac{\sin 45^{\circ}}{9}\\\\\dfrac{0.8660}{BC} = \dfrac{0.7071}{9}\\\\BC = 9 \times \dfrac{0.8661}{0.7071} = 11.02$

(ii) Find AC

$\dfrac{\sin 75^{\circ}}{AC} = \dfrac{\sin 45^{\circ}}{9}\\\\\dfrac{0.9659}{AC} = \dfrac{0.7071}{9}\\\\BC = 9 \times \dfrac{0.9659}{0.7071} = 12.29$

3. Find the perimeter

p = AB + AC + BC = 9 + 12.29 + 11.02 = 32.32

4. Find the area of the triangle

A general formula for the area of a triangle is

A = ½ab sinC

If we use ∠A, the formula becomes

A = ½ × 9 × 12.29 × sin60° = 55.30 × 0.8660 = 47.91