已知锐角(a+π/3)的终边经过点P(1,4×3^1/2),则cosa=?
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已知锐角(a+π/3)的终边经过点P(1,4×3^1/2),则cosa=?
已知锐角(a+π/3)的终边经过点P(1,4×3^1/2),则cosa=?
已知锐角(a+π/3)的终边经过点P(1,4×3^1/2),则cosa=?
r^2=2=1+48=49
r=7
cos(a+π/3)=1/7
sin(a+π/3)=4√3/7
cosa=cos(a+π/3-π/3)
=cos(a+π/3)cosπ/3+sin(a+π/3)sinπ/3
=1/7*1/2+4√3/7*√3/2
=1/14+12/14
=13/14