Question

lf sin ø=4/5 find cosø​

Answer 1

Answer:

$\huge\boxed{\cos\theta=-\dfrac{3}{5}\ \vee\ \cos\theta=\dfrac{3}{5}}$

Step-by-step explanation:

$\text{Use}\ \sin^2\theta+\cos^2\theta=1$

$\sin\theta=\dfrac{4}{5}\\\\\text{substitute}\\\\\left(\dfrac{4}{5}\right)^2+\cos^2\theta=1\\\\\dfrac{16}{25}+\cos^2\theta=1\qquad|\text{subtract}\ \dfrac{16}{25}\ \text{from both sides}\\\\\cos^2\theta=\dfrac{25}{25}-\dfrac{16}{25}\\\\\cos^2\theta=\dfrac{9}{16}\Rightarrow\cos\theta=\pm\sqrt{\dfrac{9}{16}}\\\\\cos\theta=\pm\dfrac{3}{5}$