![若tanα=13則sin^2α-sinαcosα-cos^2α=,第1張 若tanα=13則sin^2α-sinαcosα-cos^2α=,第1張](data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==)
若tanα=1/3則sin^2α-sinαcosα-cos^2α=網友廻答:
- tanα=1/3,sinα和cosα同正負
所以3sinα=cosα,9sin^2α=cos^2α,sin^2a=1/10,cos^2α=9/10
所以sinαcosa=3/10
所以sin^2α-sinαcosα-cos^2α=-11/10
網友廻答:
- sin^2α-sinαcosα-cos^2α
=(sin^2α-sinαcosα-cos^2α)/(sin²a cos²a)
=(tan²a-tana-1)/(tan²a 1) 分[fèn]子分母同時除以cos²a
=(1/9-1/3-1)/(1/9 1)
=-11/10
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