In any horoscope 1st, 5th and 9th house are known as Trines whereas 1st, 4th, 7th and 10th are known as Kendra house. First house or ascendant have dual lordship Trine and Kendra house and that is why ascendant is considered as the most important planet in any horoscope.
Any planet that have lordships of both Kendra and trine simultaneously are termed as yogkarak planets in a horoscope. Trine lord relationship with Kendra house lord is one of the potent Rajyoga one can have, especially relationship with 9th & 10th house, where 9th is the strongest trine and 10th is strongest Kendra house which is known as Dharma Karmadhipati Yoga yoga.
This also clears that not all ascendant can have yoga karaka planet and only 5 ascendant have yoga karaka planet.
1. Taurus Ascendant: Saturn lordship over 9th & 10th house.
2. Cancer Ascendant: Mars lordship over 5th & 10th house.
3. Leo Ascendant: Mars lordship over 4th & 9th house.
4. Libra Ascendant: Saturn lordship over 4th & 5th house.
5. Capricorn Ascendant: Venus lordship over 5th & 10th house.
6. Aquarius Ascendant: Venus lordship over 4th & 9th house.
Here it is seen that, the so called malefic planets Mars & Saturn are yogakaraka for 5 ascendants. Jupiter, the biggest benefic is not a yogakaraka for any ascendant.
This proves a point that in astrology one should have a dynamic approach.
A yoga karaka planet is said to produce good results of all kind like power, position, money, influence etc and is due to that fact that a yoga karaka alone works like a combination of Kendra-Trine combination.