Question 752182
A=acute angle
sin3A / sinA + cos3A / cosA = 4cos2A
I assume you meant to write given expression as follows:
{{{sin^3(A)/sin(A)+cos^3(A)/cos(A)=4cos^2(A)}}}
{{{sin^2(A)+cos^2(A)=4cos^2(A)}}}
{{{1=4cos^2(A)}}}
4cos^2(A)=1
cos^2(A)=1/4
cos(A)=1/2
A=60º or π/3