The (m,n)-ROFSs described by the degree of membership and non-membership, for which sum of m-th power of membership degree and n-th power of non-membership degree is lies between 0 and 1,is more general than the IFSs , PFSs and q-ROFSs and can describe more vague and imprecise information. In other words, the (m,n)-ROFSs can deal with the MADM and MCDM problems which IFSs, PFSs and q-ROFSs cannot and it is clear that IFSs, PFSs, and q-ROFSs are the special the (m,n)-ROFSs, which indicates (m,n)-ROFSs can be more effective and powerful tool to deal with vagueness and impreciseness involved in MADM and MCDM problems. In this section we shall propose the (m,n)-rung orthopair fuzzy cosine similarity measures and (m,n)-rung orthopair fuzzy cotangent similarity measures under (m,n)-ROFSs environment which are new extensions of the similarity measures of IFSs, PFSs and q-ROFSs.
4.1. Cosine similarity measures for (m,n)-ROFSs
In this section, a cosine similarity measure and a weighted cosine similarity measure with (m,n)-ROFSs information are created in an analogous manner to the cosine similarity measure and weighted cosine similarity measure for IFSs, PFSs and q-ROFSs.
Definition 5. Let be a fixed set. Assume = and = be two (m,n)-ROFSs of . Then the (m,n)-ROFSs cosine measure between and is defined as:
(1)
Remark 4. The cosine measures (resp. , ) for IFSs (resp. PFSs, q-ROFSs) are the special cases of cosine similarity measures of of (m,n)-ROFSs for m,n=1,1 (resp. m,n=2,2; m,n=q,q).
Proposition 2. Let and . Then the cosine similarity measure of satisfies the following conditions:
-
(i)
.
-
(ii)
.
-
(iii)
= 1.
Proof. The proofs of (i) and (ii) are obvious.
(iii) If
. Then
and
for j= 1,2,⋯ n. Thus from Equation (
1) we obtain that
= 1 □
Proposition 3.
Let and . Then the distance measure of angle defined as
Meets the specified conditions:
-
(i)
d() ≥ 0,
-
(ii)
=0.
-
(iii)
.
-
(iv)
if for any .
Proof. Proofs of conditions (i),(ii) and (iii) follows from Proposition2. (iv) Suppose that
for any (m.n)-ROFS
over
. Since Equation (
1) is a sum of terms, it is appropriate to examine the distance measures based on the angle between the vectors:
,
,
,
. Where,
For three vectors
,
,
,
in one plane, if the
,
,r. Then by triangle inequality we get that
. Combining the inequality with Equation (
1), we can get
. Hence the distance measure of angle d(
) satisfies the property (iv). □
Now we define (m,n)-ROFSs cosine measure by considering three terms membership degree(written as MD), non-membership degree(written as NMD), and indeterminacy membership(written as IMD) of (m,n)-ROFSs.
Definition 6. Let = and = be two (m,n)-ROFSs in . Then (m,n)-rung orthopair fuzzy cosine measure () between and can be expressed as:
=
Proposition 4. Consider two (m,n)-ROFSs, denoted by and , defined over . Then the cosine similarity measure satisfies the following conditions:
-
(i)
.
-
(ii)
.
-
(iii)
=1.
Remark 5. The cosine measures (resp. , ) for IFSs (resp. PFSs, q-ROFSs) are the special cases of cosine similarity measures of (m,n)-ROFSs for m,n=1,1 (resp. m,n=2,2; m,n=q,q).
Now we define the (m,n)-ROFSs weighted cosine measures between two (m,n)-ROFSs and by Considering the weighting vector of the elements in (m,n)-ROFSs.
Definition 7. Let be a fixed set and . Assume = , be the weighting vector of the elements (j = 1, 2, ⋯ ,r) satisfies the condition , ∀∈ [0, 1] and j = 1, 2, ⋯, r . Then the (m,n)-rung orthopair fuzzy weighted cosine measures and between and can be expressed as :
=
=
When we take the weighting vector = , then the weighted cosine similarity measures and will reduce to cosine similarity measures and respectively.
Remark 6. The weighted cosine similarity measures (resp. , ) for IFSs (resp. PFSs, q-ROFSs) are the special cases of weighted cosine similarity measures (k=1,2) of (m,n)-ROFSs for m,n=1,1 (resp. m,n=2,2; m,n=q,q).
Example 1.
Let and
be two (m,n)-ROFSs over . Assume m = 4, n=3 and be a weighting vector of the elements . Then = 0.8150899 and = 0.8610532.
Proposition 5. Let and be two (m,n)-ROFSs over a fixed set . Assume = , be the weighting vector of the elements (j = 1, 2, ⋯ ,r) satisfies the condition , ∀∈ [0, 1] and j = 1, 2, ⋯, r. Then the weighted cosine similarity measures (k=1,2) meets the following conditions.
-
(a)
.
-
(b)
.
-
(c)
=1.
4.2. Similarity Measures of (m,n)-ROFSs Based on Cosine Function
This section introduces several (m,n)-ROFSs cosine similarity measures between (m,n)-ROFSs, which are based on cosine function, and explores their properties.
Definition 8.
Let and
be two (m,n)-ROFSs over . Then two (m,n)-ROFSs cosine similarity measures (k=1,2) between and can be expressed as:
=
=
Proposition 6. Let and . Then the (m,n)-rung orthopair fuzzy cosine similarity measures (k = 1, 2) meets the following properties:
-
(a)
.
-
(b)
.
-
(c)
.
-
(d)
If , . Then and .
Proof. (a) The values of cosine functions lie between 0 and 1, which makes it evident.
(b) If foe any two (m,n)-ROFSs and in . Then for each j=1,2,⋯,r, and . It implies that || = 0 and || = 0. Hence =1 for k=1,2. Suppose =1,k=1,2. Then | | =0 and || = 0, for all j=1,2,⋯,r. Since cos(0) =1, there are , (j=1,2,⋯,r). Hence .
(c)Obvious.
(d) If , ∀ j=1,2,⋯,r. Then and , j=1,2,⋯,r. It follows that and . Thus we obtain that,
||≤|| ,
||≤||,
||≤|| ,
||≤||.
□
The fact that the cosine function is a decreasing function with the interval [0, ], therefor we obtain that , for k =1,2.
Next, we introduce (m,n)-rung orthopair fuzzy cosine measures based on cosine function. These measures are obtained by considering MD, NMD, and IMD for two (m,n)-ROFSs and of .
Definition 9.
Let and
be the two (m,n)-ROFSs over . Then two (m,n)-ROFSs cosine similarity measures (k=3,4) between and by considering MD, NMD and IMD can be expressed as:
=
=
Remark 7. The cosine measures (resp. , ) for IFSs (resp. PFSs, q-ROFSs) are the special cases of cosine measures (k=1,2,3,4) of (m,n)-ROFSs for m,n=1,1 (resp. m,n=2,2; m,n=q,q).
We will now introduce the (m,n)-ROFSs weighted cosine measures between two (m,n)-ROFSs, which are based on cosine functions. and by taking into account the weighting vector associated with the elements in (m,n)-ROFSs.
Definition 10. Let = and = be two (m,n)-ROFSs in and ω = be the weighting vector of the elements (j = 1, 2, ⋯ , r) satisfies the condition , ∀∈ [0, 1] and j = 1, 2, ⋯, r. Then the (m,n)-ROFSs weighted cosine measures , (k=1,2,3,4) between and on bases of cosine functions can be represented as :
=
=
() =
=
When the weighting vector , , then for k=1,2,3,4 we have (m,n)- ROFWCS = (m,n)-ROFCS.
Remark 8. The weighted cosine similarity measures (resp. , ) for IFSs (resp. PFSs, q-ROFSs) are the special cases of weighted cosine measures (k=1,2,3,4) of (m,n)-ROFSs for m,n=1,1 (resp. m,n=2,2; m,n=q,q).
Example 2.
Let and
be two (m,n)-ROFSs over . Assume m = 4, n=6 and be the weights for the elements . Then:
Proposition 7. Assume that there are any two (m,n)-ROFSs and in , the (m,n)-ROFSs weighted cosine similarity measures (m,n)- ()(k = 1, 2,3,4) should satisfy the properties (a)–(b):
-
(a)
.
-
(b)
.
-
(c)
-
.
-
(d)
If , . Then (m,n)-ROFWCS≤(m,n)-ROFWCS, (m,n)-ROFWCS≤ (m,n)-ROFWCS.
4.3. Cotangent Based Similarity Measures for (m,n)-ROFSs
Definition 11. Let and
= ,
= be two (m,n)-ROFSs. Then (m,n)-ROFSs cotangent measures and between and are defined as follows:
=
=
We will now incorporate the MD, NMD and IMD - all of which are components of (m,n)-ROFSs - to define two additional cotangent similarity measures between two (m,n)-ROFSs.
Definition 12.
Let and
. be two (m,n)-ROFSs in . Then the (m,n)-ROFSs cotangent similarity measures and between and can be expressed as:
=
() =
Remark 9. The cotangent measures (resp. , ) for IFSs (resp. PFSs, q-ROFSs) are the special cases of cotangent measures (k=1,2,3,4) of (m,n)-ROFSs for m,n=1,1 (resp. m,n=2,2; m,n=q,q).
We will now introduce the (m,n)-ROFSs weighted cotangent measures between two (m,n)-ROFSs and by taking into account the weighting vector associated with the elements in (m,n)-ROFSs.
Definition 13. Let be a fixed set and = , = be two (m,n)-ROFSs in . Assume ω = be the weighting vector of the elements (j = 1, 2, ⋯ , r) satisfies the condition , ∀∈ [0,1] and j = 1, 2, ⋯, r.
Then the (m,n)-ROFSs weighted cotangent measures (k=1,2,3,4) between and are expressed as follows:
=
=
=
=
When we let weighting vector = , then coincides with , for k=1,2,3,4.
Example 3.
Let and
be two (m,n)-ROFSs over . Assume m = 5, n=7 and = 0.25, = 0.35 and =0.40 be the weights for the elements .Then:
Remark 10. The weighted cotangent similarity measures (resp. , ) for IFSs (resp. PFSs, q-ROFSs) are the special cases of weighted cotangent measures (k=1,2,3,4) of (m,n)-ROFSs for m,n=1,1 (resp. m,n=2,2; m,n=q,q).