已知tanx=2,求2/3乘以sinx方+1/4cosx方的值

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已知tanx=2,求2/3乘以sinx方+1/4cosx方的值

已知tanx=2,求2/3乘以sinx方+1/4cosx方的值
已知tanx=2,求2/3乘以sinx方+1/4cosx方的值

已知tanx=2,求2/3乘以sinx方+1/4cosx方的值
=2/3*sinX^2/(sinx^2+cosx^2)+1/4*cosx^2/(sinx^2+cosx^2)
=2/3tanx^2/(tanx^2+1)+1/(4(tanx^2+1))
=2/3*4/5+1/(4*5)
=8/15+1/20
=35/60
=7/12

把要求的试子除以(sinx方+cosx方)...再上下除掉tanx方..代进去算....就可以了~~~要是选择或填空就画个直角三角形...直角边是2和1的..然后代进去算