Identitas dan Rumus Trigonometri

sin²θ + cos²θ = 1

1 + tan²θ = sec²θ

1 + cot²θ = csc²θ

Ruas kiri : $$\left(\sin x+\cos x\right)^2$$

$$\left(\sin x+\cos x\right)^2=\sin^2x+2\sin x\cos x+\cos^2x$$

$$=\sin^2x+\cos^2x+2\sin x\cos x$$

$$=1+2\sin x\cos x$$

ruas kiri = ruas kanan

terbukti

sin A · cot A = cos A

csc θ = 1/sin θ

Benar

sin θ / (1 - cos θ) = (1 - cos θ) / sin θ.

$$\cot\theta=\frac{\cos\theta}{\sin\theta}$$

Nilai sec θ adalah 1/cos θ = -5/4.

sin²θ + cos²θ = 1

1 + cot²x = csc²x.

Nilainya adalah 0,64

$$1-\sin^2x=\cos^2x$$

$$\Longleftrightarrow1-\sin^2x=\left(0,8\right)^2$$

$$\Longleftrightarrow1-\sin^2x=0,64$$