10C4 represent the Combinations of 10 objects taken 4 at a time.
The formula for nCr is:

In the given case, n=10 and r=4. Using these values we get:

This means we can make 210 combinations of 10 objects taken 4 at a time.
Answer:
42.78⁹, 137.22⁹.
Step-by-step explanation:
sine Ф=0.6792
Angle Ф in the first quadrant = 42.78 degrees.
The sine is also positive in the second quadrant so the second solutio is
180 - 42.78
= 137.33 degres.