设a为二象限角,tan(a+π/4)=1/2,求sina+cosa的值
问题描述:
设a为二象限角,tan(a+π/4)=1/2,求sina+cosa的值
答
解由a为二象限角,tan(a+π/4)=1/2知a+π/4仍为二象限角,则由sin²(a+π/4)+cos²(a+π/4)=1即tan²(a+π/4)+1=1/cos²(a+π/4)即cos²(a+π/4)=1/(tan²(a+π/4)+1)=1/((1/2)...