论文部分内容阅读
1另一类特殊角的三角函数值的计算我们知道,30°、45°、60°等是一类特殊角。还有一些角,如15°、75°、22.5°、67.5°等这样的角,事实上也具有一定特殊性。我们暂且可以把它称为另一类特殊角。现在,我们试讨论这另一类特殊角的三角函数值的计算问题。(1)15°和75°角的三角函数值的计算。如图1,在Rt△ABC中,设∠A=15°,∠ABC=75°。为了计算∠A和∠ABC的三角函数值。不妨设BC=1。在AC上取点D,使DB=DA,联结DB。由图1知,∠BDC=30°,容易得出DB=DA=2,
1 Calculation of Trigonometric Function Values for Another Special Angle We know that 30°, 45°, 60°, etc. are a special type of angle. There are also some corners, such as 15°, 75°, 22.5°, 67.5°, and so on, which in fact also have certain characteristics. For the time being, we can call it another special kind of angle. Now, we try to discuss the calculation of the trigonometric function value of this other special kind of angle. (1) Calculation of trigonometric function values for 15° and 75° angles. As shown in FIG. 1, in RtΔABC, let ∠A=15° and ∠ABC=75°. In order to calculate the trigonometric function of ∠A and ∠ABC. May wish to set BC=1. Take point D on AC and let DB=DA join DB. From Figure 1, we know that ∠BDC=30°, it is easy to get DB=DA=2.