Draw a right triangle in which the sine of x (opposite over adjacent) is 4/5. Since you need to find the adjacent side (other leg of the right triangle), use the Pythagorean theorem:
b^2 + 4^2 = 5^2
b = 3
Therefore, cos x = adjacent/hypotenuse = -3/5 (Cosine is negative since the angle is in the second quadrant, where cosine is negative)
b^2 + 4^2 = 5^2
b = 3
Therefore, cos x = adjacent/hypotenuse = -3/5 (Cosine is negative since the angle is in the second quadrant, where cosine is negative)
-
In a right triangle, the sin of an angle is the length of the side opposite it divided by the length of the hypotenuse. So if you draw this triangle, you know that its hypotenuse is 5 units long and one of its other sides is 4. The cosine is the side length adjacent to angle x (the third side, lets call it side "a") divided by the hypotenuse. So this question is asking you to use the length of side "a" and divide it by the length of the hypotenuse (5 units). So use the Pythagorean theorem to find side "a":
a^2+4^2=5^2
a=3
and divide by the hypotenuse.
The exact answer will therefore be cosx=3/5.
a^2+4^2=5^2
a=3
and divide by the hypotenuse.
The exact answer will therefore be cosx=3/5.
-
easy q
-
cos x = -3/5 since x is in 2nd quadrant.