求值:sin135° — cos105° — tan180° +cot 45°
- 2022-09-12
sin135° — cos105° — tan180° +cot 45°
=√2/2-cos(60°+45°)-0+1
=√2/2-√2/4+√6/4+1
=(√2+√6+4)/4
左邊=sin²α×tanα+cos²α×cotα+2sinαcosα =sin^2α*sinα/cosα+cos^2αocsα/sinα+2sinαcosα =sin^4α/sinαcosα+cos^4α/2sinαcosα+4sin^2αcos^2α/2sinαcosα =(sin^2α+cos^2α)^2/sinαcosα =1/sinαcosα右邊=tanα+cotα =sinα/cosα+cosα/sinα=(sin^2α+cos^2α)/sinαcosα=1/sinαcosα