Question

WILL FAN AND MEDAL FOR ANSWER.
7.
If sinθ=4/5, what is the value of cosθ in quadrant 1?
A.
9/25
B.
16/25
C.
3/5
D.
5/4

Answer 1

careful here

Answer 2

it is not \[\sin^2(4/5)+\cos^2(x)=1\] it is \[(\frac{4}{5})^2+\cos^2(x)=1\]

Answer 3

easier to draw a right triangle

Answer 4

there is a picture of an angle whose sine is \(\frac{4}{5}\) find the missing side via pythagoras, or just remember the mother of all right triangles 3 - 4 - 5
then you can take any trig ratio you like

Answer 5

Thank you for pointing out my mistake.