急求解 初三数学题目－关于三角函数的，在线等

sinA=BC/AB=0.7 所以AB=BC÷0.7=50/7 由勾股定理得：AC=5√5
所以cosA=AC/AB=7√5/10 tanA=sinA/cosA=√5/5

sin^A+cos^A=1
则cos^A=0.51
cosA=0.71
tanA=sinA/cosA=0.99

解:
∵CB:AB=7:10,CB=5
∴AB=50/7
∴AC=√(50/7)^2-5^2=5√51/7
∴cosA=5√51/7:50/7=√51/10
tanA=5:5√51/7=7√51/51

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By killua
Is it complete eough?

B
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C A
sinA=BC/AB=0.7=7/10
设sinA=7x/10x=0.7,则7x=5所以x=5/7
则AC=√((10x)^2-(7x)^2)=(√51)X=(√51)*7x
故cosA=AC/AB=(7√51)/10
tanA=BC/AC=(7√51)/51

回答完毕,够详尽了,给我分吧*^_^*

cosa=0.8 tana=0.75