Question

sin58sin13+cos58cos15

Answer 1

given question is in the form of
cos(A–B) = sinAsinB+cosAcosB
so in the given question clearly A=58° B=13°
cos(58-13) = cos45° = 1/√2
hence the answer is 1/√2

Answer 2

We know that,

cos(A-B) = cosAcosB+sinAsinB .

sin58sin13+cos58cos15

= cos(58-13)

= cos(45)

= $\frac{1}{ \sqrt{2} }$

Hope helped!