Question

Sa se calculeze cos(A+B), cos(A-B) daca: sinA=3/5, sinB=5/13, A, B apartin (0, π/2)

Answer 1

sin <a+sin<b=3/5 +5/13=   39+65/65=104/65
cos (a+b)=1/sin(a+b)= 1 supra 104/65= 65/104
cos(a-b)=1/sin(a-b)=1 supra 39-65/65=  1 supra -26/65=  - 65/26= -5/2