Evaluate the expression given cos a=4/5 for 0<a<pi/2 and sin b=-15/17 for 3pi/2<b<2pi. SHOW WORK 1.sin(a+b)
answer must equal -36/85

2.cos(a-b)
answer must equal -13/85

3.tan(a+b)
answer must equal -36/77

4.tan(a-b)
answer must equal -84/13

its an acute right triangle

step-by-step explanation:

step-by-step explanation :

we know that

the measurement of the outer angle is the semi-difference of the arcs which comprises

in this problem

m< xzy is the outer angle

substitute the values

the measure of angle xoy is equal to

> by central angle

substitute the value