export function isArray(arr: any): arr is any[] | ArrayBufferView<ArrayBufferLike>;
export function multQuatVec(quat: any, vec: any): any;
export function normRad(angle: any): number;
export function acos(fValue: any): number;
export function multiplyMat3Mat3(matLeft: any, [mat0, mat1, mat2]: [any, any, any]): any;
export function multiplyMat3Vec(matLeft: any, { x, y, z }: {
    x: any;
    y: any;
    z: any;
}): any;
export function multiplyVecMat3(vecLeft: any, [column0, column1, column2]: [any, any, any]): any;
export function multiplyVecMat4(vecLeft: any, [column0, column1, column2, column3]: [any, any, any, any]): any;
export function isNumber(nr: any): boolean;