The formula to calculate the area of the shaded piece(A) is,
![Area\text{ of shaded portion = }Area\text{ of the sector - Area of the triangle}](https://img.qammunity.org/2023/formulas/mathematics/college/itq8sroqjpoep22ftjaw30cup0aopqxen7.png)
The formula for the area of the sector(A1) is,
![A_1=(\theta)/(360^0)*\pi r^2](https://img.qammunity.org/2023/formulas/mathematics/college/txcvw5abd1dt3d6d7cu9qom7tjuy7lwsdj.png)
Given
![\begin{gathered} \theta=90^0 \\ r=radius=4m \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/ww6iu2fp7uzojnz9fkm9l720tlh0i36fml.png)
Therefore,
![\begin{gathered} A_1=(90^0)/(360^0)*\pi\text{\lparen4\rparen}^2=4\pi \\ \therefore A_1=4\pi m^2 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/y3jnp8h927piycsigt9hznn2p780fcvc4t.png)
The formula for the area (A2) of the triangle is,
![A_2=(1)/(2)absin\theta](https://img.qammunity.org/2023/formulas/mathematics/college/oc1xf605yuvt93st6qqa6ugndjx9c5hxro.png)
Given
![\begin{gathered} a=4m \\ b=4m \\ \theta\text{=90}^0 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/4421ab7lwzfsel6z0kzn1gyytc5m0h0oqq.png)
Therefore,
![\begin{gathered} A_2=(1)/(2)*4*4* sin90^0=8sin90^0=8 \\ A_2=8 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/50i4vhpfbwciylkjnbdyfhq6m5tosnkldm.png)
Therefore, the area of the shaded piece(A) is
![A=4\pi m^2-8m^2=4\left(\pi-2\right)m^2](https://img.qammunity.org/2023/formulas/mathematics/college/2a45e38at1ieh7gt8zyxqghjpm1d878sp0.png)
Hence, the answer is
![4\left(\pi -2\right)m^2](https://img.qammunity.org/2023/formulas/mathematics/college/g5i3qg8irlw3k8yv53d0thnjpz0szryv7u.png)