Question 80913
verify that cos(pi/2 + x)=-sinx
The sum formula that applies here is:
{{{highlight(cos(x+y)=cos(x)*cos(y)-sin(x)*sin(y))}}}
Another important thing to remember is {{{cos(pi/2)=0}}} and {{{sin(pi/2)=1}}}
{{{cos(pi/2+x)=cos(pi/2)*cos(x)-sin(pi/2)(sin(x))}}}
{{{cos(pi/2+x)=0*cos(x)-1*sin(x)}}}
{{{cos(pi/2+x)=0-sin(x)}}}
{{{cos(pi/2+x)=-sin(x)}}}
Happy Calculating!!!!