Trig Identities
There are some formulas you can get from trigonometry ratios.
We already know the pythagorean theorum works for the triangle we create on unit cicle because it is a right triangle. Also, we know that cos and sin is each x and y value, and also, the length of base and adjacement.
Pythagorean Theorum-h²=b²+p²
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h=1
b=cosΘ
p=sinΘ
1²=cos²Θ+sin²Θ
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We got one formula. 1²=cos²Θ+sin²Θ. From here, we can make some other formulas.
Divide the equation by cos²Θ. What happen?
What about divide by sin²Θ?
Finally, I got two more formulas.
1. sec²Θ = 1 + tan²Θ
2. csc²Θ = 1 + cot²Θ
If you have anything that want me to explain more or if you have any questions, please leave it on this page.
cos²Θ | it is same as (cosΘ)²