Can someone help solve this, thanks. Let a, β, y be the three interior angles of any triangle, try to prove that cos(a+β+y)= -1.​

Given:

are three interior angles of any triangle.

To prove:

Solution:

Angle sum property of a triangle: According to this theorem the sum of all three interior angle of a triangle is always 180 degrees.

It is given that, are three interior angles of any triangle.

By using the angle sum property of triangles, we get

             ...(i)

We need to prove,

Taking LHS, we get

               [Using (i)]

Hence proved.

total amount to be paid = $19.5

step-by-step explanation:

given ,

original price = $25.99

discount = 25%

discount amount = 25% of original price

discount amount = 25/100   * 25.99

discount amount = $6.49

hence , the total amount to be paid = original price - discount amount

                                                            = $25.99 - $6.49

                                                            =$19.5

total amount to be paid = $19.5

whatvare the choices

step-by-step explanation: