Apr 22, 2018 · This means that if you want to deduce what $\cos (90^\circ)$ should be, you need to make sure that the adjacent side is not just adjacent to the angle $\alpha$, but also to the …

Dec 28, 2019 · 三角函数是在 直角三角形 里给出定义的, 当 斜边 保持不变时,随着角度的增大,这个角的 对边 也在增大,邻边在减小; 当角度变为90度时,这个角的对边与斜边相等,邻边缩小为0, …

Jun 27, 2019 · More explanation - sin and cos are complementary to each other, that's where the name came from - sine and cosine . Complementary angles in a triangle are x and 90-x.

Jul 31, 2019 · 0 How are these reduction formulas derived? $$\sin (90°+θ) = +\cos (θ)$$ $$\cos (90°+θ) = -\sin (θ)$$ The source of the formula. I understand how to reduce angels that fall …

May 15, 2014 · Let's set $\alpha$ to 45 (around where it appears to be in the diagram) and find the cosine value, thus giving us the green line. $$\cos (45) = 0.5$$ Fair enough. $\cos …

Take the sin x and cos (90-x) and you will see they will be the same). You also know that cos (w)=cos (-w) (you can see why this is by imagining w and -w on the unit circle).

Apr 8, 2019 · Now let's try to find the sine of $\left (\frac\pi2 + \theta\right)$ radians, that is, the sine of $90$ degrees plus $\theta$ radians.

The trigonometric ratios of an angle greater than $90^\\circ$ are equal to the supplementary angle's ratios. I'm just clarifying this, but the ratios don't actually exist for angles greater than …

Jun 14, 2020 · 我的建议是，其他乱七八糟的衍生公式不要被太多，牢记住这三类最基本的原始公式表达式和特征（比如当你看到sin和cos相乘时，脑子里要立刻反映出来包含这个特征的有和 …

sin 30°＝cos60°＝½ sin60°＝cos30°＝√3／2 sin45°＝cos45°＝√2／2 tan 45°＝1 tan30°＝√3／3 tan60°＝√3 其实sin30，45，90和cos30,45,60数值的顺序是相反的，3倍tan30°＝tan60° …