Given that cos (a + b) = - 1 / 3, cos 2A = - 5 / 13, a and B are obtuse angles, find sin (a-b)

Given that cos (a + b) = - 1 / 3, cos 2A = - 5 / 13, a and B are obtuse angles, find sin (a-b)

cos2a=-5/13
ninety

In the triangle ABC, the opposite sides of angles a, B and C are ABC, and a = 1, C = √ 2, COSC = 3 / 4 (1) find sin (a + b) (2) find sin a (3) find vector CB × vector ca

The side opposite the triangle angle ABC is ABC, COSC = 1 / 5. Find the value of sin (c + 45 degrees). The vector of Ca multiplied by CB = 1, a + B = root 37, find the side C and triangle face

What do you mean by sin (c + 45)
2. Because ca * CB = 1.. so. Abcosc = 1, COSC = 1 / 5. So AB = 5. According to the coxuan theorem, it is easy to get C2 = A2 + b2-2abcosc = (a + b) 2-2ab-2abcosc, so C2 = 37-2 * 5-2 = 25. So C = 5

In the triangle ABC, the side opposite the angle ABC is ABC, COSC = 1 / 5, and the value of sin (c + 45) is obtained. If the vector of Ca · CB = 1A + B = root 37, the value of side C is obtained

2. Because ca * CB = 1.. so. Abcosc = 1, COSC = 1 / 5. So AB = 5. According to the coxuan theorem, it is easy to get C2 = A2 + b2-2abcosc = (a + b) 2-2ab-2abcosc, so C2 = 37-2 * 5-2 = 25. So C = 5Ps: write the first question in detail. I'll help you see