他的护照证明了他的身份。

His passport proves his ___identity.

他们在兴趣爱好的相似性令人惊讶。

The ___similarity in their hobbies was surprising.

在三角函数中，sin²θ + cos²θ = 1 是一个重要的恒等式。

In trigonometry, sin²θ + cos²θ = 1 is a fundamental ___identity.

她的艺术风格是构成她个人身份的重要组成部分。

Her artistic style is a key part of her ___identity.