Buktikan identitas berikut 1. 5 cos kuadrat A = 5-5 sin kuadrat A

Identitas
[tex]5cos^{2} A = 5 - 5sin^{2} A[/tex]
[tex]5cos^{2} A + 5sin^{2} A= 5 [/tex]
[tex]cos^{2} A + sin^{2} A= 1 [/tex]

pembuktian identitas

misal ada segitiga abc,dengan sudut A
a = depan sudut
b = samping sudut
c = miring / hipotenusa.

[tex]cos A = \frac{b}{c} [/tex]
[tex]b = c.cos A [/tex]

[tex]sin A = \frac{a}{c}[/tex]
[tex]a = c.sin A [/tex]

kalau di subtitusi ke rumus phytagoras

[tex] a ^{2} + b^{2} = c^{2} [/tex]
[tex] (c.sin A) ^{2} + (c.cos A )^{2} = c^{2} [/tex]
[tex] c^{2} .sin A ^{2} + c^{2} .cos A ^{2} = c^{2} [/tex]
[tex] sin A ^{2} + cos A ^{2} = 1[/tex]

fyuh..