Tan is positive in the first quadrant, and the third quadrant.
cos is positive in first and fourth quadrant.
Which makes Theta in third quadrant (tan positive, cos negative). Sine therefore must also be negative.
Draw the triangle, legs 7 and 13, determine the hypotenuse, then sine.
If tan(theta)=7/13 and cos(theta)<0, what is the exact value of sin(theta)?
1 answer